You can get an idea of the different print runs within the print groups by the print defects found on some of the subjects in the same print group.
Here are the stats on a few print group 1 subjects that have front print defects that are found with 350 backs. None of these defects are found with a 150 series back.
I put the EPDG's in to show that they were printed with the 150 backs and not the 350 backs you can also get an idea of what backs were probably printed together in a print run.
Stats Clarke.jpg
Stats Dougherty.jpg
Stats Hinchman.jpg
Stats Keeler.jpg
Stats Killian.jpg
Stats Schlei.jpg
Stats Tannehill.jpg
I would guess that there were 2 or 3 print runs of the PD350's and 1 or 2 print runs for the rest of the 350 print group 1 backs. The stats show that the Old Mills and SC350/25's were most likely printed together but not with the Sov 350's.