Armenius M-8 was manufactured in Zella St Blasii in 1919 and in Zella Mehlis.
Model 8 is a hammerless .320 or 7.65mm auto (.32acp) revolver, five shot, with a 50mm or 140mm barrel and folding trigger and it looks like you got one!
Friedrich Pickert, Armenius Waffenwerk produced a wide range of pocket revolvers prior to 1945, available in a wide variety of of barrel lengths, cylinder capacities and calibers. Although of obsolete design they were cheap and very well made. Most are standard commercial cartridge only I am not sure how much luck you will have in finding the .320 as I have never looked for that cal.