Introduced in 1918, the Model 51 was developed from patents and designs from John D. Pederson of Pederson Device and Irwin-Pederson fame as a straight blowback semi-automatic pistol with multiple overlapping safety features and good ergonomics. With rare exceptions, the "PA" prefix is seen throughout the pistol's production run, making "PA2" one of the earliest known examples. Fixed sights, with the two-line address (ending in "PEDERSEN'S PATENTS PENDING") on top of the slide, "PA2" on the left side of the frame, and "REMINGTON/UMC/TRADE MARK" in circles on the checkered and riveted grips. With a copy of a Remington Society of America article discussing serial number "2", a pistol suspected of being a factory prototype.

Excellent, with 90% of the original blue finish, showing some light scratches near the takedown pin, bright edge wear and scattered handling marks. The grip safety shows a mixed brown patina, and is bright on the sides. The grips are fine, with a lighter brown color to the right grip panel and a few scratches. Mechanically excellent.