that is a German Company which is no longer building real guns.
Schmidt is the family name of the company owner(s).
Ostheim is the little town in northern Bavaria close to the former border with communist East Germany ( therefore companies were heavily subsidized by the West German Government. Rhon, actually Rhoen, is the geographical name for that forested high plains area ( very good hunting area ).
Them .22 single action revolvers had been produced since the sixties.
They had been in the affordable price range, approx. 100 USD in the seventies. They were sold all over Germany and the US.
The material was nevertheless very good quality.
And the sixshooters had been very accurate.My cousin used to have one in Germany.
With the introduction of gun registration and limited access to handguns in particular since 01.01.1973 in Germany, all companies producing recreational guns perished over the next 20 years.
Also H. Schmidt is no longer producing real firearms.
They went into the blank pistol business, if not already bankrupt.
You will not get any info, let alone spare parts from that company.