delivered the opinion of the Court:
On hehalf of Weston, a vigorous attack is made upon the sufficiency of this evidence to show conception and reduction to practice, under the burden of proof imposed upon Thomson not only by the prior patent of his rival, but also by his long inaction and delay.
That the instrument, which was produced during the taking of the testimony, was in fact constructed, as claimed, there can be no reasonable doubt. Whatever of doubt there may be, as aifecting Thomson’s claim, would seem to relate exclusively to the point of actual, successful reduction to practice. The question involves something of matter of opinion as well as of matter of fact. It is this: Whether, considering the failure to bring the instrument into use either in the private plant for which it was originally designed, or in connection with any other practical construction, as well as the delay in applying for a patent by an inventor and a manufacturer engaged in patenting and utilizing, generally, all inventions in this art, the test in the private laboratory of the inventor failed to demonstrate the practical utility of the machine, as then adjusted, and caused it to be regarded and abandoned as an experiment, for the time at least.
It is quite true, as contended by'the appellee, that great stress has frequently and justly been laid upon circumstances of private and partial test and long delay thereafter, as indicating, with certainty, nothing more than an unsatisfactory, experimental use, when subsequently brought forward to overcome the patent of a diligent inventor in the same field who has not only given the benefit of his discovery to the public through the Patent Office, but also through manufacture and general introduction into commercial use. Traver v. Brown, 14 App. D. C. 34; Warner v. Smith, 13 App. D. C. 111, 113; *378Appert v. Schmertz, 13 App. D. C. 117, 130; Fefel v. Stocker, 17 App. D. C. 317, 321; Reichenbach v. Kelly, 17 App. D. C. 333, 344; Latham v. Armat, 17 App. D. C. 345, 353.
This question — whether the evidence, in the light of all the attendant circumstances, was sufficiently strong to establish, beyond doubt, the fact of actual reduction to practice, under the rule applied in the cases cited, need not now be determined.
The Commissioner expressly waived it and, assuming the fact of reduction to practice, denied priority to Thomson upon another and distinct ground.
Concurring in his conclusion upon that ground, we will follow the course pursued in his decision.
That conclusion is, that Weston, although later than Thomson in conception and reduction to practice, is nevertheless an inventor and entitled, as such, to an award of priority because of the deliberate concealment by Thomson, from the public, of all knowledge of his invention and use.
The facts relating to the action of Thomson are fairly summarized by the Commissioner as follows:
“ After Thomson made his instrument in 1894 he placed it in his model-room, or private laboratory, to which outsiders were not admitted, and this instrument was only seen by the employees who might go into that room, and the knowledge of this instrument and its use in the model-room was confined to Thomson and his assistant, Shand.
“ The use to which Thomson put this device, whatever it ■may have been, was in his private model-room. The public was not made acquainted with the instrument or its use and derived no benefit whatever from it. It seems that he did not attach sufficient importance to it to take steps to obtain a patent, and he believed that it was not patentable. He deliberately concealed the invention from the public until another had patented the device and put it into extensive use.”
As held by the Commissioner, the foregoing facts bring the case directly within the operation of the doctrine enounced in Mason v. Hepburn, 13 App. D. C. 86.
*379In that case it appeared that Mason had conceived the idea of the gun-clip in controversy, had made it and applied it to a completely-finished gun, and that the gun had then been put away in the model-room of the Winchester Arms Company, which employed Mason and was entitled to the benefit of his inventions. The gun was probably tested in the shooting-gallery of the company.
Knowledge of these facts was confined to the inventor and a few other employees of the company who had access to the model-room. Further test of the clip, than as stated above, was treated as immaterial; in fact what was done was regarded as answering the substantial requirements of the law in respect of the reduction to practice of such a device.
What was then said of the effect of that action is directly applicable to the facts under consideration in the present case:
“Although the construction and adaptation to use of the clip were within the knowledge of several persons, these were all, with Mason himself, employees of the Winchester Repeating Arms Company, for whose benefit the invention was made. They had either been called on to aid in the construction and use, or by the nature of their employment, were necessarily cognizant of it. The invention was therefore as much secreted from the public as if it had been confined to the knowledge of Mason alone. Pennock v. Dialogue, 2 Pet. 1, 19; Kendall v. Winsor, 21 How. 322. The public did not, and was not intended to receive any benefit from it during the seven years that intervened between the construction and the application for the patent. 13 App. D. C. 91.”
It is true that the time of concealment in this case was something less than four years as against seven years in that. The mere difference in time, however, is not sufficient to affect the application of the principle, for it is as certain in one case as in the other that the application for the patent was solely stimulated by the publication of the patent granted to another inventor. No substantial or even plausible excuse for Thomson’s inaction is disclosed by the testimony.
*380Again in Mason v. Hepburn, after quoting the statement of the “ true policy and ends of the patent laws,” made in Kendall v. Winsor, 21 How. 322, 327, it was said:
“ Considering, then, this paramount interest of the public in its bearing upon the question as presented here, we think it imperatively demands that a subsequent inventor of a new and useful manufacture or improvement who has diligently pursued his labors to the procurement of a patent in good faith and without any knowledge of the preceding discoveries of another, shall, as against that other, who has deliberately concealed the knowledge of his invention from the public, be regarded as the real inventor and as such entitled to his reward. Id., p. 95.”
In support of this proposition, many decisions of the courts and of Patent Commissioners were cited. Since then the practice of the Patent Office has been governed by the rule as declared and the principle has been reasserted by us in several decisions. Warner v. Smith, 13 App. D. C. 111, 115; Esty v. Newton, 14 App. D. C. 50, 53; In re Mower, 15 App. D. C. 144; McBerty v. Cook, 16 App. D. C. 133, 139; Fefel v. Stocker, 17 App. D. C. 317, 322; Reichenbach v. Kelly, 17 App. D. C. 333, 343.
It is true that in the majority of the above cases the decisions went upon another ground, but the principle was involved and was restated, and may be regarded as settled as far as it can be by this court.
What was said in McBerty v. Cook, supra, and has been referred to on behalf of the appellant, namely, that “the rule will not be extended to any case not coming clearly within it,” was not to impair its force but to recall attention to the restricted field of its application.
The particular object of the beneficence of the patent law is the individual who first conceives, and with diligence perfects an invention. And where one has completed the act of invention his right to the reward in the form of a patent becomes complete save in two instances that.may be satisfactorily shown to exist. Hirst, he loses the right as against the public in general by a public use for the statutory period. *381Second, by deliberate concealment or suppression of tbe knowledge of bis invention be subordinates bis claim, in accordance witb tbe general policy of tbe law in tbe promotion of tbe public interest, to tbat of another and bona fide inventor wbo during tbe period of inaction and concealment shall have given tbe benefit of tbe discovery to tbe public. Viewed in tbe light of “ tbe true policy and ends of tbe patent laws,” tbe latter is tbe first to invent, and therefore entitled to tbe reward. As said in Mason v. Hepburn:
“ Tbe true ground of tbe doctrine, we apprehend, lies in tbe policy and spirit of tbe patent laws and in tbe nature of tbe equity tbat arises in favor of him wbo gives tbe public tbe benefit of tbe knowledge of bis invention, wbo expends bis time, labor and money in discovering, perfecting and patenting, in perfect good faith, tbat which be and all others have been led to believe has never been discovered, by reason of tbe indifference, supineness or wilful act of one wbo may, in fact, have discovered it long before.”
Tbe concealment of tbe appellant in this case having been deliberate and without reasonable excuse, tbe Commissioner was right in awarding priority to bis opponent, and bis decision will be affirmed. It is so ordered, and tbat tbe clerk certify this decision and tbe proceedings herein to tbe Commissioner of Patents as provided by law. Affirmed.