VAN ORSDEL, Associate Justice.
This interference involves an invention relating to an electric lighting and engine starting system described in the single count of the issue as follows:
“The combination of an engine, an electric machine connected thereto, a secondary battery, an automatic switch for controlling the charge of the battery by the electric machine, and a switch for cutting out the automatic switch and connecting the battery to the electric machine, whereby the same may be operated as a motor for starting the engine.”
Bonine filed his application July 7, 1911, on which a patent was granted April 16, 1912. Bliss filed his application June 25, 1910.
[1] The tribunals of the Patent Office unanimously found on the issue of fact that Bliss was the first to conceive and reduce the invention to practice. The rule that we will not disturb such a finding, except for palpable error, applies with exceptional force to this case. No other reasonable conclusion could have been reached from the evidence.
[2] The further contention that the application of Bliss did not amount to a constructive reduction to practice is without merit. It is settled by repeated decisions of the courts that the filing of an allowable application constitutes a reduction to practice. Porter v. Louden, 7 App. D. C. 64, 72; Davis v. Garrett, 28 App. D. C. 9; Telephone Cases, 126 U. S. 2, 535, 8 Sup. Ct. 778, 31 L. Ed. 863.
[3] The question of whether or not an application is allowable, and *990one upon which the issuance of a patent can be predicated, is primarily for the experts of the Patent Office, and will not be inquired into in this sort of a proceeding except for manifest error. “The rule of the Patent Office' that the filing of an allowable application is constructive reduction to practice is only the expression in another form of the rule that the application of a patented invention, if it sufficiently describes the invention, is conclusive evidence that the invention was made at least as early as that date.” Automatic Weighing Mach. Co. v. Pneumatic Scale Corp., 166 Fed. 288, 92 C. C. A. 206.
The decision of the Commissioner of Patents is affirmed, and the clerk is directed to certify these proceedings as by law required.
Affirmed.