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 hesitation-locked 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 "PA23" one of the earliest known examples. Fixed sights, with the two-line address (ending in "PEDERSEN'S PATENTS PENDING") on top of the slide, "PA23" on the left side of the frame, and "REMINGTON/UMC/TRADE MARK" in circles on the checkered and riveted grips.

Very fine as possibly factory refinished, with 85% of the quality blue finish, showing some light edge wear, minor scratches, and some pitting beneath the surface. The grips are good, with deep scuffs just above the Remington-UMC marking and some other minor handling marks. Mechanically very good.