Mike, you're absolutely correct that most if not all of the Pipefitters served their apprenticeships. These subcontractors were all union men and this was considered a premium job so the locals sent their best men. Ditto most of the other locals too, but I'm most familiar with the Pipe-Fighters and Electricians.
I got into a 'discussion' on another forum about full-penetration welds, and it appears to me that very few gun folks have ever seen a truly GOOD welder's work. Some of these guys are EXTREMELY artistic and creative as well as quite demanding of their own personal skills; witness some of their truly spectacular handmade and bespoke belt buckles! 'Government work' of course, but IMO their expertise more than made up for any personal projects done on company time. When these guys finished a job, you KNEW that it was done by a professional taking pride in his work.
IMO the ACGG is kinda like a union hall in the sense that whoever belongs is almost always at least competent. Maybe not the best but supposedly not the worst either. Of course we've all seen even some Guild members' work that smacked of what Ackley called 'fearful turkeys', but then others' work is IMO the epitome of elegance and grace as well as flawless performance.
IMO internet forums like this one have done MUCH to weed out the crooks and charlatans but also IMO the rest of us are too quick to give a pass to substandard work. We don't want to hurt anyone's feelings so we don't tell folks that the smith they're planning to use is a doofus with all the refined taste of a space alien and the mechanical ability of a gorilla.
True craftsmanship isn't dead yet but it's become all too rare and now we hafta HUNT for it!
Regards, Joe