This is an extraordinary example of a very rare, one of only 100, Springfield Model 1888 "Positive Cam" trapdoor rifles that was manufactured in 1888. The "Positive Cam" rifle was an attempt by Springfield Armory to modify the Springfield trapdoor breech block to eliminate the occasional failure of the locking cam mechanism. The "Positive Cam" rifles featured a modified breech block marked "U.S./MODEL/1888". The breech block has the screw that retains the firing pin located on the right side behind the thumb piece rather than on the underside. The "Positive Cam" itself is part of the breech locking device. By a cramming or wedging action, a firmer lock was created for the breech block, taking all loose play out of it. All known examples of the only 100 "Positive Cam" rifles are in the 400,000 to 416,000 serial number range and the stocks of all the rifles have the "SWP/1888" inspection cartouche. This rifle is in the correct serial number range and has the correct configuration breech block, correct breech block markings, receiver relief cut on the right side for cam shaft clearance and "SWP/1888" cartouche. The rifle has the standard blade front and Buffington rear sights and iron ram rod with slotted button head. The lock is marked with the eagle shield motif followed by "U.S./SPRINGFIELD" ahead of the hammer, the left side breech end of the barrel is marked with the "V/P/eagle head" inspection marks, with an unrecognizable marking next to that and an "A" on top. Mounted with a smooth full one-piece walnut stock with the boxed "SPW/1888" cartouche on the left wrist, a small "O" and circled script "P" behind the tang and "U.S." marked buttplate tang. The Springfield "Positive Cam" rifles are one of the rarest variations of the Springfield trapdoor rifles. The 100 "Positive Cam" rifles were issued to the San Antonio Arsenal for testing. Most of these rifles subsequently were issued to active units in Texas, New Mexico and Arizona where they saw active service.