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 "7" an uncommon example, possibly very early production. one of the earliest known examples. Fixed sights, with no address marking on top of the slide, "7" on the left side of the frame, and "REMINGTON/UMC/TRADE MARK" in circles on the checkered grips.

Fair showing 75% of the period refinished blue, with areas of brown and gray patina, scattered scratches and mild spotting. The grips are fair, with a mended break in the bottom of the left panel. The magazine well safety is disabled, otherwise mechanically very good.