Originally Posted by
Hsing-ee
I think they are 11mm if I can remember back 20 years ... The Weihrauchs had 13mm dovetails until the late 1970s, and the Hammerlis did too, can't remember any other 13mms from those days. Rhino and Apel did make 13mm mounts I am sure, but most were the 11mm ones.
For real authenticity, most people used two-piece mounts as the one-piece jobs were very expensive (£25, just under half the price of a new HW35 from a discount house) and these usually meant having an arrestor block as well, fitted behind the rear mount. You can still get them I think from Chambers, Knibbs or Manchester Air Guns.