delivered the opinion of the Court:
We will first consider the tri-party interference. Dement took no testimony, and relies upon the date of filing his application, January 9, 1904, for constructive reduction to practice, Peters alleges conception of the invention on January 1, 1904, and disclosure February 11, 1904. He filed his application April 14, 1905. Hopkins claims conception and disclosure in October, 1902, and reduction to practice December 1, 1908. His application here in interference was filed April 9, 190G, and, for convenience, will hereafter be referred to as “Application No. 4.” Hopkins had filed three prior applications,— “Application No. 1,” January 14, 1904; “Application No. 2,” September 24, 1904; and “Application No. 3,” March 10, 1905. The third application purports to contain improvements dis*309closed in “Application No. 2.” “Application No 4” is merely a consolidation or grouping of the matters contained in the earlier applications.
The Examiner of Interferences awarded priority to Hopkins, and the Board of Examiners-in-Chief and the Commissioner reversed this holding, and awarded priority to Dement, all the tribunals holding against Peters. A careful review of the record impels us to concur in that finding. In no view of the case can Peters bo declared a prior inventor. He altempts to establish a date of conception about January 1, 1904, hv his own testimony and that of another witness. This witness is uncertain as to the exact date, and this is important, since Dement filed nine days after the earliest date of conception claimed by Peters. There is nothing in the testimony of Peters or his witness to indicate that he disclosed the means by which the object of the invention was to be attained. Giving the testimony full credit, Peters had only a vague conception that a certain result could be obtained, without disclosing means for its accomplishment. On the other hand, conceding to Peters, 'for the purpose of argument, everything he claims as to his interview with his corroborating witness, he cannot claim the benefit of a disclosure prior to February 11, 1904, the date of disclosure alleged in his preliminary statement, and this would bring him more than a month after Demerit’s filing date. Without further reviewing the evidence, Peters will he eliminated from the case, and the investigation will he directed to the respective claims advanced by Hopkins and Dement. Dement lias a single date, January 9, 1904, upon which he must stand or fall. With Peters out of the case, and Dement relying wholly upon his filing date, we will proceed to review Hopkins’s case as disclosed in the record.
Contrary to the view of the tribunals of the Patent Office, wo think Hopkins’s case revolves about his first machine, known in this case as “Exhibit Machine No. 1.” All of the tribunals found this machine, as exhibited in evidence, to he a physical embodiment of the invention, and it was conceded to be such by counsel at bar. With the general concession that all the *310counts of the issue can be read on to this machine, an examination of Hopkins’s proof as to its construction is most essential.
It appears that work was begun on tbe construction of this machine about September 4, 1903, and that it was built largely in accordance with Hopkins’s exhibit drawings 1 to 15, from which his “Application No. 1” was prepared.
Hopkins testified with reference to his “Exhibit Machine No. 1” as follows :
. Q. Was that machine ever completed?
A. It was.
Q. When was the adding mechanism thereof in such a stage of completion that it could be operated to demonstrate its practicability ?
A. About the middle of December, 1903.
Q. Are you the H. Hopkins whose name appears on the payroll book beginning with page 91 thereof (Hopkins’s Exhibit B) testified to by Mr. Sharp ?
A. I am.
Q. When the machine was operated, or rather the adding mechanism thereof, about the middle of December, 1903, was such operation successful or otherwise?
A. It was successful.
Q. Who was present when the machine was first operated at that time ?
A. Mr. Thieme, Mr. Whitelaw, myself, my brother, and, I believe, J. C. Moon.
Q. Where was the machine first operated ?
A. At the Landis Machine Company shop, located at 25th and Mullanphy streets, St. Louis, Missouri.
Q. In what manner was the machine operated at that time ?
A. To demonstrate its ability to add and also to transfer a number.
Q. Please explain how you transfer a number, and in' your explanation please state what parts are operated'and in' what manner they control or affect other parts ? ■ !
A. In the machine there are two sets of adding wheels, inde*311pendently operated by a single cam, and means for shifting the cam into operative relation with either of the two sets of am cumulafor wheels. To effect this shift of the operating cam a key is provided marked “R,” which shifts the operating cam from one to the other position. In transferring a total from the forward to the rear totalizer, the total key for the forward accumulator is depressed and also “R” key, which shifts the operating cam into operative relation with the accumulator, then pulling the handle which actuates the actuating devices, causing the forward totalizer to he set at zero. Before the return movement of the actuator the rear totalizer is brought into operative relation with and on the return movement of the rack bars the number is transferred to-the rear accumulator wheels. In transferring a number from the rear totalizers only the produce or “P” key for the rear totalizer is depressed, and the machine operated in the usual manner. This transfers the total from the rear to the forward totalizer.
Q. Was the machine operated to transfer a number from the front to the rear totalizer, and vice versa, in the manner described in your last answer, in December, 1903 ?
A. It was.
Q. Was that machine at that time provided with printing mechanism 2
A. It only had the type on it at that time, but the printing hammers were not. The parts for the hammer section were mostly-made at that time.
Q. When were the printing hammers added to the machine ?
A. I think they were added during the early part of January, 1904.
Q. When was the typewriting mechanism added to the machine ?
A. According to my recollection, it was in the early part of February, 1904. T never kept'any record of these matters, but speak from memory.
Q. Where is that machine now 2
A. It is here before me,
*312Q. Is the adding mechanism of that machine the same to-day as it was when you operated it in December, 1903 ?
A. It is.
•It should be remembered that the printing and typewriting mechanism are not here involved.
As to the conception and • successful operation of the adding mechanism, ITopkins is corroborated by the witnesses Thieme and W. W. Hopkins, who worked upon the construction of the machine, and Crawford and Moon, who were present and saiv it operated. Thieme and W. W. Hopkins, as well as the inventor, were highly skilled in this art. They testified that at the December, 1903, trial of the adding mechanism of the machine, they operated it; and they fully explained in their testimony the manner in which it operated. One Sharp, the bookkeeper of the Landis Machine Company, prodxiced the pay-roll, showing payments for work done on this machine beginning September 1, 1903. On the whole, we think this evidence is amply sufficient to establish both conception and reduction to practice. “To hold that this was not done would he arbitrarily to disregard and set at naught the testimony of witnesses whoso character and reputation are unimpeachcd, and whose testimony is reasonable and in entire harmony with the circumstances of this case. We are unwilling to assume such a position.” Boynton v. Taggart, 40 App. D. C. 82.
It appears that, after the completion of “Exhibit Machine No. 1” by the attachment of the typewriting mechanism in February, 1904, Hopkins immediately began the construction of another machine embodying the counts of the issue. It also contained the multiplying mechanism described in Hopkins’s ‘Application No. 4,” but not involved in this issue and not appearing in his “Application No. 1.” This machine was completed in September, 1904, just before he filed his “Application No. 2.” It also appears that Hopkins constructed five more machines containing the issue -in interference between September, 1904, and the early part of 1906, completing the last one about three months prior to the filing of his “Application No. 4.” *313The .Board of Examiners-in-Chief, in its opinion, speaking of Hopkins’s diligence and achievements up to September, 1904. the date of the completion of his second machine and the filing of his second application, said': “Certain it is that at no time during this period did Hopkins relinquish in any way his efforts to perfect his invention. During a portion of the time, his efforts were no. less than prodigious. We marvel at the amount of work that this man and his associates accomplished between the first, of March and end of September, 1904. The machine-which he undertook to construct is not only complicated, but the inventive ideas involved therein are extremely ingenious, and their embodiment required the evolution of many details of construction and the greatest skill in workmanship.”
No two of the tribunals of the Patent Office are in accord as to ITopkins’s “Application No. 1.” The Examiner of Interferences' held that it disclosed an operative machine containing the issue of this interference, hut held that Hopkins’s testimony was insufficient as to the completion and test of “Exhibit Machine No. 1.” ITe awarded priority to Hopkins on the ground that his first application was a constructive reduction to practice, and that it was executed prior to Dement’s filing date, and therefore established conception in Hopkins as of the date of its execution. The Board of Examiners-in-Chief found that the device disclosed in “Application No. 1” is inoperative in six particulars, and therefore not a constructive reduction to practice, and that Hopkins’s evidence is insufficient to establish when the “Exhibit Machine No. 1,” was completed or tested. The Commissioner of Patents reversed the hoard as to. certain of the features of inoperativeness, hut held that there is no testimony establishing the date of completion of Hopkins’s “Exhibit Machine No. 1,” and that there is no testimony as to when said machine was successfully operated.
It is inconceivable upon what hypothesis the tribunals of the Patent Office ignored the conclusive proof as to the construction, completion, and successful operation of Hopkins’s “Exhibit Machine No. 1.” It will not do to discredit by wholesale the testimony on these crucial points of -witnesses skilled in the *314art, and, so far as the record discloses, entitled to the highest credit.
In Seeberger v. Russel, 26 App. D. C. 344, we held that, quoting from the syllabus, “Where the inventor, * * * and two witnesses who show themselves thoroughly familiar with its construction, testify fully as to the construction and operation of the device, and state that they used it a number of times and found it successful, a reduction to practice is sufficiently proved, and it is unnecessary that the facts on which they base their conclusion as to the successful working of the device should appear on the record.”
It is sought to impeach the testimony of some of the witnesses by certain technical errors disclosed in their cross-examination as to the tests made on this “Exhibit Machine No. 1” in December, 1903. Hopkins’s witnesses, however, stand unassailed in witnessing to the fact that work on this machine was begun about September 1, 1903, and that the machine was completed in February, 1904, in all particulars as it appeared in evidence, concededly containing the issue of this interference. Convinced that a successful test was made in December, 1903, we are little concerned with its exact nature or extent, since the machine was .completed in the exact form in which it appeared in evidence. On this theory of the case, Hopkins had conceived the invention in issue, had reduced it to practice, and was busily engaged in pushing the machine to completion when Dement entered the field.
It is urged that Hopkins by filing his application here in interference abandoned his former applications. Eor the sake of argument, let us brush aside Hopkins’s applications Nos. 1, 2, and 3, and we find him conceiving the invention in September, 1903, and between that date and January, 1906, completing in rapid succession seven machines, ■ and within three months after the completion of the last of these seven machines, each of which contained the invention in issue, filing his “Application No. 4,” here in interference. As suggested in the brief of counsel, there was not an unreasonable length of time elapsed between January 1, 1906, the date of the completion of the last *315of the seven machines, and April 9, 1906, the date of filing his fourth application. The device is a most complicated one, involving great inventive genius, and requiring a high degree of skill to describe in detail its wonderful mechanism. The fourth application contained thirty-six sheets of drawings, seventy-five typewritten pages of specifications, and four hundred and thirteen claims. Hence, lack of diligence cannot be imputed to Hopkins in filing this application, even if there had been no actual reduction to practice, since he had been vigorously pushing his invention to a perfect completion from the date of conception in September, 1903, to the date of filing his fourth application.
But we think “Application No. 4” in no way signified an abandonment by Hopkins of his former applications. It was intended as a general substitute for the former applications. .Referring to “Application No. 1,” it is contended that it is difficult to explain its failure to disclose the issue of the interference, if, as Hopkins claims, he had a machine containing it at the date of filing the application. It is stipulated that the Patent Office drawings which accompanied the first application were made between July and October, 1903, by one Dillon. It is not strange, therefore, if the application did differ in some details from the machine in which the adding mechanism was not completed for two months, and the machine itself was not completed until four months, after the drawings were made. It not infrequently occurs that, in a complicated mechanism like this, the original application is incomplete and has to be subjected to amendment. A court, however, will not deprive an inventor of the fruits of his invention upon fine-spun technicalities touching the inoperativeness of his device as disclosed in the application, when it conclusively appears that at the time of filing the application he had a machine showing the invention.
Finding, as we must, that Hopkins has conclusively proved conception of the invention of the issue not later than September, Í 903, the operativeness or inoperativeness of the device disclosed in “Application No. 1” becomes unimportant, since, on *316any angle from which we view the case, his right to priority is legally established.
The case of Peters v. Hopkins, 34 App. D. C. 141, can be disposed of very briefly. The earliest date of conception claimed by Peters is about January 1, 1904. Hopkins antedates this by several months, and, as we have held in the former case, diligently reduced his invention to practice. He must therefore be adjudged entitled to the award of priority.
The decision of the Commissioner in cases No. 869 and No. 871 is reversed, and the decision in case No. 872 is affirmed. The clerk is directed to certify these proceedings as by law required. Nos. 869 and 871 Reversed, and No. 872 Affirmed.
A petition for a rehearing was overruled February 2, 1914.