concurring.
While I concur both in the conclusion reached and in the reasoning expressed in the majority opinion, I write to express my additional views on the experimental use doctrine and to observe that on this record the facts make this a much closer case than the majority opinion might suggest.
I
The experimental use doctrine permits an inventor to conduct testing to refine his invention without losing the right to obtain a patent, even if such testing occurs in the public eye. Pfaff v. Wells Electronics, Inc., 525 U.S. 55, 64, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d 1641, 1645 (1998). The experimental use doctrine arose as an exception to the traditional rule that an inventor loses the right to a patent if he puts the invention in public use or on sale before filing a patent application. Id., quoting Pennock v. Dialogue, 27 U.S. (2 Pet.) 1, 24, 7 L.Ed. 327 (1829) (“[h]is voluntary act or acquiescence in the public sale and use is an abandonment of his right.”). Congress codified the traditional rule as the “public use” and “on-sale” statutory bars of 35 U.S.C. § 102(b) and included in the statutory scheme a one-year grace period. The experimental use doctrine survived as a common law exception to those statutory bars. Pfaff, 525 U.S. at 64-65, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646. The experimental use exception preserved the right to a patent if the purpose of a use made of an invention outside the one-year grace period was experimental as opposed to commercial:
It is sometimes said that an inventor acquires an undue advantage over the public by delaying to take out a patent, inasmuch as he thereby preserves the monopoly to himself for a longer period than is allowed by the policy of the law; but this cannot be said with justice when the delay is occasioned by a bona fide effort to bring his invention to perfection, or to ascertain whether it will answer the purpose intended. His monopoly only continues for the allotted period, in any event; and it is the interest of the public, as well as himself, that the invention should be perfect and properly tested, before a patent is granted for it. Any attempt to use it for a profit, and not by way of experiment, for a longer period than two years before the application, would deprive the inventor of his right to a patent.
Elizabeth v. Am. Nicholson Pavement Co., 97 U.S. 126, 137, 24 L.Ed. 1000 (1877).
The experimental use exception was, over time, reformulated as experimental use “negation” of the statutory bar of § 102(b), in which the burden of persuasion does not shift at any time to the patentee. See TP Labs., Inc. v. Prof'l Positioners, Inc., 724 F.2d 965, 971, 220 USPQ 577, 582 (Fed.Cir.1984) (“it is incorrect to impose on the patent owner ... the *1355burden of proving that a ‘public use’ was ‘experimental.’ These are not two separable issues. It is incorrect to ask: “Was it public use?’ and then ‘Was it experimental?’ Rather, the court is faced with a single issue: Was it public use under § 102(b)?”). A “totality of the circumstances” test was used to determine whether the use was experimental or commercial in character. See Western Marine Electronics, Inc. v. Furuno Elec. Co., 764 F.2d 840, 845, 226 USPQ 334, 337-38 (Fed. Cir.1985) (“the court will want to consider the totality of the circumstances relating to the character and extent of commercial activities, ... along with the character and extent of bona fide experimentation”). However, the “totality of the circumstances” test was discredited by the Supreme Court, and, with respect to the on-sale bar, replaced with a two-part test. Pfaff, 525 U.S. at 66-67 & n. 11, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646-47 & n. 11.
The test announced by the Supreme Court in Pfaff set forth two conditions for application of the on-sale bar: “[fjirst, the product must be the subject of a commercial offer for sale.... Second, the invention must be ready for patenting.” 525 U.S. at 67, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646-47. The Supreme Court explained that the second prong is satisfied by either (a) “proof of reduction to practice before the critical date,” or (b) “proof that prior to the critical date the inventor had prepared drawings or other descriptions of the invention that were sufficiently specific to enable a person skilled in the art to practice the invention.” Id. at 67-68, 119 S.Ct. 304, 48 USPQ2d at 1647. The first prong of the Pfaff test focuses on the commercial characteristics, if any, of the individual transaction. A resolution of the first prong depends on an objective assessment of the facts surrounding the transaction. The inventor’s subjective intent to experiment is not sufficient. See Paragon Podiatry Lab., Inc. v. KLM Labs., Inc., 984 F.2d 1182, 1186, 25 USPQ2d 1561, 1564 (Fed.Cir.1993) (citing TP Labs., 724 F.2d at 972, 220 USPQ at 583 (“the expression by an inventor of his subjective intent to experiment, particularly after institution of litigation, is generally of minimal value”)). In contrast, the second prong focuses on the invention as a whole, implicating the invention’s stage of development. It is only after the development of the invention has progressed to the stage where it is “ready for patenting,” that the second prong of the Pfaff test can be said to be satisfied.
Before Pfaff, reduction to practice was a central focus of both the on-sale bar and experimental use negation thereof. See, e.g., Seal-Flex, Inc. v. Athletic Track & Court Constr., 98 F.3d 1318, 1324, 40 USPQ2d 1450, 1454 (Fed.Cir.1996). The coincidence of reduction to practice as a focal point for both aspects brought a symmetry, and often a simplicity, to the analysis. An invention could be the subject of an experimental use anytime up to reduction to practice. RCA Corp. v. Data Gen. Corp., 887 F.2d 1056, 1061, 12 USPQ2d 1449, 1453 (Fed.Cir.1989). Once reduced to practice, the invention could not be the subject of an experiment that would negate an on-sale bar. Atlantic Thermoplastics Co., Inc. v. Faytex Corp., 5 F.3d 1477, 1480, 28 USPQ2d 1343, 1346 (Fed.Cir. 1993). Conversely, an invention seldom would trigger an on-sale bar prior to the time it was reduced to practice. Because events that might be experimental in nature were only those occurring prior to the time the invention in question was reduced to practice, i.e., only during the experimental stage leading up to a reduction to prac*1356tice, the distinction between a sale made for experimental purposes and a sale made during the experimental stage of an invention’s development was often more academic than real.
After Pfaff, the coincidence of the transitional event of reduction to practice as a focal point for both the on-sale bar and the experimental use doctrine changed. What Pfaff made clear is that the triggering event for an on-sale bar is not reduction to practice, but the advancement of the invention to the stage where it is “ready for patenting.” Because nothing in Pfaff altered the transitional significance of reduction to practice for experimental use negation, the heretofore complementary nature of the two tests and the symmetry that such congruence brought to the analytical framework disappeared. Traversing this new landscape now demands in each case a careful examination of the purpose of the use contemplated in a potentially barring sale, not merely that the invention then may be in an experimental stage, and signals a shift in focus from the second prong to the first in evaluating experimental use negation.
Pfaff changed the test for when an on-sale bar is triggered, but it did not change the experimental use doctrine or the timing or nature of events giving rise to an experimental use exception. “The law has long recognized the distinction between inventions put to experimental use and products sold commercially.” Pfaff, 525 U.S. at 64, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1645. The Supreme Court stated that application of the on-sale bar of § 102(b) continues to turn on whether the inventor’s use of the invention was commercial or experimental. Id. at 64-65, 525 U.S. 55, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1645 — 46. In particular, the Court discussed the experimental use doctrine in connection with the first part of the Pfaff test in evaluating whether the invention was the subject of a commercial offer for sale:
The experimental use doctrine, for example, has not generated concerns about indefiniteness, and we perceive no reason why unmanageable uncertainty should attend a rule that measures the application of the on-sale bar of § 102(b) against the date when an invention that is ready for patenting is first marketed commercially. In this case ... there is no question that the sale was commercial rather than experimental in character.
Pfaff, 525 U.S. at 67, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646-47.
It bears repeating that what is important to an assessment of the commercial versus experimental significance of a sale is not necessarily the posture of the invention’s overall development, but the nature or purpose of the particular use to which the invention that is the subject of that sale is to be put. See Manville Sales Corp. v. Paramount Sys., Inc., 917 F.2d 544, 550, 16 USPQ2d 1587, 1592 (Fed.Cir.1990) (“a sale that is primarily for experimental purposes, as opposed to commercial exploitation, does not raise an on sale bar”); U.S. Envt’l Prods., Inc. v. Westall, 911 F.2d 713, 716, 15 USPQ2d 1898, 1901 (Fed.Cir.1990) (“[a] section 102(b) bar is avoided if the primary purpose of the sale was experimental”); Barmag Banner Maschinenfabrik AG v. Murata Mach, Ltd., 731 F.2d 831, 839, 221 USPQ 561, 567 (Fed.Cir.1984) (quoting In re Theis, 610 F.2d 786, 793, 204 USPQ 188, 194 (CCPA 1979) (“[t]he experimental exception applies only if the commercial exploitation is merely incidental to the primary purpose *1357of experimentation to perfect the invention”)).
Thus, the question posed by the experimental use doctrine, assessed under the first prong of the two-part on-sale bar test of Pfaff, is not whether the invention was under development, subject to testing, or otherwise still in its experimental stage at the time of the asserted sale. Instead, the question is whether the transaction constituting the sale was “not incidental to the primary purpose of experimentation,” i.e., whether the primary purpose of the inventor at the time of the sale, as determined from an objective evaluation of the facts surrounding the transaction, was to conduct experimentation. Scaltech, Inc. v. Retec/Tetra, L.L.C., 178 F.3d 1378, 1384 n. 1, 51 USPQ2d 1055, 1059 n. 1 (Fed.Cir. 1999). As noted, once the invention is reduced to practice, there can be no experimental use negation. Zacharin v. United States, 213 F.3d 1366, 1369, 55 USPQ2d 1047, 1050 (Fed.Cir.2000); RCA Corp. ., 887 F.2d at 1061,12 USPQ2d at 1453. But up to that point, regardless of the stage of development of the invention, and quite apart from the possible satisfaction of the second prong of the Pfaff test, the inventor is free to experiment, test, and otherwise engage in activities to determine if the invention is suitable for its intended purpose and thus satisfactorily complete. Furthermore, because the statutory bar of § 102(b) is evaluated on a claim-by-claim basis, the fact that an additional feature covered in a dependent claim may result from the sale of an invention covered in a parent claim does not mean that the parent claim may escape a statutory bar based on that sale. See Lough v. Brunswick Corp., 86 F.3d 1113, 1122 n. 5, 39 USPQ2d 1100, 1107 n. 5 (Fed.Cir.1996) (“[e]ach claim of the patent must be considered individually when evaluating a public use bar.”).
In determining whether a use is commercial versus experimental, this court has considered a variety of factors relevant to the first part of the Pfaff test, including: (1) the necessity for public testing, (2) the amount of control over the experiment retained by the inventor, (3) the nature of the invention, (4) the length of the test period, (5) whether payment was made, (6) whether there was a secrecy obligation, (7) whether records of the experiment were kept, (8) who conducted the experiment, and (9) the degree of commercial exploitation during testing. See Baker Oil Tools, Inc. v. Geo Vann, Inc., 828 F.2d 1558, 1564, 4 USPQ2d 1210, 1214 (Fed.Cir.1987). We have also considered: (10) whether the invention reasonably requires evaluation under actual conditions of use, (11) whether testing was systematically performed, (12) whether the inventor continually monitored the invention during testing, and (13) the nature of contacts made with potential customers. See Seal-Flex, 98 F.3d at 1323, 40 USPQ2d at 1453-54.
While the Supreme Court in Pfaff discarded the “totality of the circumstances” test for determining the existence of an on-sale bar, 525 U.S. at 66 n. 11, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646 n. 11, nothing in the Supreme Court’s opinion suggests that a weighing of the factual submissions of the parties, particularly on the first prong of the Pfaff test, is precluded. See Weather chew, Corp. v. J.L. Clark, Inc., 163 F.3d 1326, 1333-34, 49 USPQ2d 1001, 1007 (Fed.Cir.1998) (weighing facts in applying Pfaff). To the contrary, the balancing of such facts lies at the heart of what has been termed “experimental use negation.” See TP Labs., 724 F.2d at 971, 220 USPQ at 582.
II
In the present case, there is no genuine issue of material fact in dispute as to the *1358satisfaction of the second prong of the Pfaff test. The dock prototypes covered by claim 1 were far more than “drawings or other descriptions of the invention” and were sufficiently specific “to enable a person skilled in the art to practice the invention.” See Pfaff, 525 U.S. at 67-68, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1647; Robotic Vision Sys., Inc. v. View Eng’g, Inc., 249 F.3d 1307, 1312-13, 58 USPQ2d 1723, 1726 (Fed.Cir.2001). Thus, the only question is whether Schafer presented enough evidence to meet its burden on the first prong; i.e., to show by clear and convincing evidence, resolving all reasonable doubts in favor of EZ Dock, that the single sale to Mr. Greden was a commercial sale not incidental to the primary purpose of experimentation.
On the facts presented, I think this is a much closer case than the majority opinion might suggest. The evidence of record makes it difficult to conclude that the primary purpose of the sale to Mr. Greden was experimentation. The sale to Mr. Greden was a commercial sale of an existing structure without assurances demanded or obtained by the seller that the docks would remain at Bass Camp for any length of tune or would be subjected to any sort of test in the turbulent water conditions later asserted to be important. There were no limitations placed on the use to be made of the docks by Mr. Greden or his father. There were no requirements that the docks remain at the location where the docks were originally placed. There were no restrictions to prevent re-sale, and no effort to impose on Mr. Greden, Mr. Gre-den’s father, or any transferee any obligation to assist or permit testing of any sort. There were no particular tests contemplated nor a period of time envisioned over which the tests would be undertaken. None of the evidence presented by either party shows control by the inventors over this alleged “experiment.” “[A] use cannot be experimental if the inventor failed to maintain sufficient control over the invention and its testing.” Lough v. Brunswick Corp., 103 F.3d 1517, 1526, 41 USPQ2d 1385, 1393 (Fed.Cir.1997) (declining suggestion for rehearing en banc) (Michel, J., dissenting); Paragon, 984 F.2d at 1187, 25 USPQ2d at 1565. See also Rooklidge and Jensen, Common Sense, Simplicity and Experimental Use Negation of the Public Use and On Sale Bars to Patentability, 29 J. Marshall L.Rev. 1, 29 n. 144 (1995). The record in this case not only fails to show “sufficient control,” it is devoid of any control by the inventors after the sale transaction was consummated.
The majority opinion points out that Mr. Greden initiated the purchase in the absence of any commercial marketing activity by the inventors, did not pay full market price for the dock, and received free installation and free repair services. But those facts are just as consistent with an arms-length commercial sale as they are with an experiment apparently undefined in scope or extent. I concur in the result only because the case is before us on summary judgment and we must view the evidence in a light most favorable to the non-movant, here EZ Dock. It is therefore appropriate that we return the ease to the fact finder for a more complete assessment of the relevant facts and a more thorough weighing of the evidence bearing on Schafer’s burden to show by clear and convincing evidence that the sale to Mr. Greden was a commercial sale not incidental to the primary purpose of experimentation.