I started off as a trained watchmaker
If I ran a store and was going to hire a Gunsmith trainee, given the choice of a watch maker and a GS school trainee......I'd go for the watch maker.
It he can build parts I can't even see, think of the precission gun parts he could build.
A good machinest can build/fix anything. Just think about it, anyone can thread a barrel shank, but how many can thread a watch stim for a itty bitty ladie's watch. Heck I can't ever read the face numbers on some of my wife's watches.