Sir, you have a modestly priced Diana 2 which was made after world war 2. They are a smooth bore pistol of low power 300 fps or less. They were often used for shooting BB or darts. They are often called a Gat pistol.
I bought one for a friend at Little Rock show, often they sell for $50 range.
Make sure it has the screw at rear of action where BB is loaded.
Pre war versions are very nice, all metal, no wood grips. They have diana huntress impressed in metal grips.
I am a bit of a Diana collector and buy and sell air gun literature. I have a magazine with a nice historical and how it works article on the Diana 2.
Drop me an email if interested.
Doug Law
dlaw1940@yahoo.com
http://www.bigspringguns.net