Hi there. If its a 1930's model the date should be stamped on the butt end of the stock...2.38 is February 1938. They were available in .177, .22 and .25 cal. What sights are fitted ? May be other calibres but I have not come across them.The .25 was a smooth bore...pretty rare and I am lucky enough to own a really nice one. The stock should be Walnut from my experience . They may also come in Beech ??...the later models were Beech. Manufactured in Germany. Well worth spending some money on as they are really nice to shoot...the internal engineering is excellent ....BUT they are not 12 ft/lb power... more like 7 to 8. I'm no expert but I do like the German Diana/Original air rifles/pistols. Value....Really n ice one £100 may be £120 . Average ...say £70. The prices are only based on my experience.
Garvin on the BBS forum is a bit of a Diana/Original guru....