Makers' marks will certainly help some, but you will often find a gun with a maker's mark on the barrels, nothing but standard proofmarks on the flats and water table. That will tell you who made the barrels (if you can decypher the mark), but you can't assume that the barrelmaker made everything else. In fact, chances are excellent that he didn't.
Since all the European countries had a gunmakers' guild, and since "guild" guns seem to be defined as guns that were not made "in house" in a factory--and either bear no name or only the name of a gun shop or dealer, not a gunmaker--then "guild" seems to be about as accurate a description as could be conveyed concisely.
