Question about 15GP22 production
Does anyone have concrete information as to when exactly commercial production of the 15GP22 began, and when it ended?
I know the developmental tubes in the Model 5s were built starting in November of 1953. I'm assuming commercial production of the 15GP22 started in late December 1953 or early January of 1954, and probably lasted maybe six-ish months at most? And about when was hand welding of the ultor flange abandon in favour of automated welding?
My good 15GP22 was manufactured the 13th week of 1954; I'm trying to determine if this tube was hand or machine welded.