Just one thing I'd like to add to the discussion. Neither Matska, nor Maslov, nor Alyoshkin, not any other Russian gunmaker would benefit anything from faking English proofs on the guns they sold under their own names. At their time, the Russian public believed that a "best" gunmaker should turn out every part of his guns himself. Having guns made by the trade was seen as inferior. "If he gets them from England" - the customer would reason - "I might as well get the original". The guns of bespoke St. Petersburg gunmakers were priced above the market - you could buy a similar BLE by Webley&Scott or W.W.Greener for about 2/3 of the price, and a quality Belgian or German gun would cost even less. So, the more work the gunmakers put in their guns, the more valuable they would be in the eyes of their customers.