That one has got me too. All my books only list marks applicable to the C.I.P. (Permanent International Commission for the Proof of Small Arms). So that rules out Germany, Austria, Belgium, Czechoslovakia, France, Hungary, Yugoslav, (the usual suspects). So I'm wondering if it is one of the other European countries that are not C.I.P. registered such as Denmark or the Netherlands. They will have some sort of Proof House but not one with acceptable standards to be C.I.P. registered. I'm sure someone will come up with something. As a last resort send photos to one of the British Proof Houses http://gunproof.com/ for clarification as someone there is bound to know and they are there to assist. Lagopus.....