I still think the difference between Panyetaire and Serraller resides only in the idiomatic attribution to the trade.
Although Panyetair is specificaly a gun lock maker, Serraller (Serralheiro in Portuguese) defines a lock smith in general; hoewever for this specific case, meaning a gun lock smith.
... But Fernando K is right, TRADUTORE = TRADITORE, an allusion i often quote myself
