Welcome to the forums from the Wiregrass, Ohop! I do not know the meaning of those marks. However, someone should be along shortly to help. In the interim, check the gun for military markings as follows:

Military markings include “U.S.” on butt, cartouche on grips, and “L” and “P” on barrel and cylinder, and frame marked “L”.

(SCSW, 4th Ed., Page 113).

You may need a magnifying glass as the letters are very small, IIRC. If you can't find the military markings, except perhaps the P on the frame, you may have a civilian version of which only 650 were made.

__________________
Guy
SWHF #474 SWCA LM#2629