Speaking of "size of presses available for stamping," there is an NdeM 40' box #76079 in Volume 7 of Classic Freight Cars. The caption says it was built a few months after this list's era ends (March 1961) but I can ask if there were cars with this kind of end built earlier? At first glance it looks like a typical R-3/4 end of the mid-50s and later, but the lack of intermediate ribs at two places instead of one suggests that it was made in 3 panels instead of two. Hence my R-1/3/3 designation. Cars of that height had been getting two-section ends for over 25 years by then.
