The original manufacturer of these pistols was Rhoner Sportwaffenfabrik, in Germany, but they went out of business in 1999; another company has bought the rights to produce these pistols, though, and you might be able to get some info from them:
SM Chemnitzer Sportwaffen- und Munitionsfabrik GmbH (Blankenauer Str. 75, D-09113 Chemnitz/Germany, Tel. +1149-371 418353
They are a pretty simple design, though, pretty similar to most of the older single-shot bolt-action 22 rifles. HTH.