That is PARKER GUN WORKS OVERLOAD PROVED. Typically used in the Remington era. We start seeing it in the 236xxx - 237xxx range. The left barrel flat carries a Remington date code of DG, D = September, G = 1938, surrounded by three typical Remington inspector stamps. The right barrel flat has the typical Parker Bros. V in a circle steel mark and 3 7 weight stamp.