All, thanks for all the replies so far. Very interesting. I thought I would add that there are numbers/letters under the barrel (you can kind of see them in the picture where the 192G shows up) that I can make out better in the larger pics that I have. They are:
P16___65.9,75 S.P.28,5 BL

The underline after the 6 is about 2 or 3 spaces wide. Not quite sure about the P at the front or the 9. Don't currently have the gun here to double check.

I've seen some mention of the cavemen stamps. What is their significance?

The story behind the gun is my dad was into antiques/guns and he picked this up a long time ago at a gun show. He was very proud of it. He passed many years ago and the gun has been sitting in its case at my moms. I'm not really into guns so its time to let a collector enjoy this.

Bill