Sorry to hear about your father. Welcome to the forum.
From your description, you've properly IDed your 922 as a 1st Model 5th Variation (1940 - 1947.) Wartime commercial H&R handguns are very SCARCE. I've seen or heard about only a handful during my years of collecting H&Rs. Apparently, H&R, during slack time from producing war goods, put a few pieces together, most likely from parts made before 1942. The numbers stamped on the side of the cylinder are the remnants of Patent numbers covering the "SAFETY RIM" cylinder and the "RICE" type, bird's head shaped grip frame. The roll stamp seems to have been wearing out for a number of years and H&R simply used it until there was nothing legible being stamped any longer.
When H&R began using the year code letter system - the letter code was followed by a sequential numeric which indicates the gun's manufacture number and not associated with the model. So, your gun was the 7679th hand gun produced in 1944, not necessarily all M922s. Not knowing how many commerial handguns were produced during that year, it is nearly impossible to pin down a date or month of production.