There were some early Lefevers with the recessed hinge pin, and several of the J. Stevens Arms & Tool Co. doubles had a slightly recessed hinge pin.
There was just a bit of drama over Parker Bros. Trojan Grade's forearm fastening --
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being a patent infringement of the A.H. Fox Gun Co.'s Patent No. 1,029,374 granted to J.C. Kremer & A.H. Fox on June 11, 1912. After the A.H. Fox Gun Co. quit using the Baker J-spring forearm on their The Sterlingworth Company guns, and the Sterlingworth became an A.H. Fox Gun Co. gun, they went to using the J.C. Kremer & A.H. Fox forearm fastening on their extractor Sterlingworths and their extractor small-bores of all grades.
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They used their F.T. Russell Patent No. 1,029,229 forearm fastening on their ejector Sterlingworths and their ejector small-bores of all grades.
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Several decades ago, before I was quite so focused on this historical minutia, Babe DelGrego showed me a file of letters he had between Parker Bros. and A.H. Fox Gun Co. about this. Unfortunately I don't recall any details of the letters, but we know that the A.H. Fox eventually quit using their J.C. Kremer & A.H. Fox type fastening and went to using the F.T. Russel style on both extractor and ejector guns.
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