Well, production started in 1942, went to Aug 45, 811,119 were made. 39,999 were made in 38 S&W, rest were .38 S&W Special. It was made in a 2, 4,5, and 6 inch version. Front sight should be rounded over, half-moon shape. Thee should be a lanyard loop on the butt. It would appear that barrel has been shortened, and different front sight, so value AS A COLLECTIBLE dropped sharply.
The were made for the US Govt, and were issued to some pilots, guards at War production plants, etc. The govt inspector was Guy H. Drewry, whose initials you see on your revolver.
Many of these went to Great Britain as part of lend-Lease, and were proof tested as the Brits did with all firearms. BNP is the proof mark for Birmingham Nitro Proof. So yours has been over the pond and back- you've got a veteran there!
What we have here is... failure- to communicate.