Some information here.
Just found This old pistol , can anybody tell me anything about it ?
Mile Oak Shooting Club
Some information here.
Vintage Airguns Gallery
..Above link posted with permission from Gareth W-B
In British slang an anorak is a person who has a very strong interest in niche subjects.
As far as I know: dates from 1933 - 1945 with maybe 50,000 being made each year. classed as a 'target pistol'... made by Mayer & Grammelspacher of Rastatt, Germany. DRP equates to 'Deutches Reichs Patent. Most likely rifled barrel but some smoothbores were made. Does not appear to be particularly valuable (sorry). May well have a 'D' mark on the cylinder rather than the 'Diana' full name. Very similar to the Slavia ZVP pistol.
Cheers, Phil