I just noticed that the modern small heads have two different numbers on the face. One number on the top left and another on the lower right. This seems to exist on both the 50s and 100s I have dated starting in the 1960s. I'm assuming that the lower right number is the plate number. What does the number on the top left signify?
Depends on what you want to do with them. When I'm trying to work out the print runs on some older series where the BEP records are incomplete (or on some recently printed stars where the BEP's being very slow about issuing production reports), the plate positions are critical and the plate numbers are pretty much irrelevant. If you're collecting certain printing varieties, then vice versa. At least one of the big TPGs would list that $50 note as "position G", rather than the correct "position G3". For any notes printed in 32-subject sheets, that number is an essential part of the plate position designation.
Ah yes! I assumed the letter was the position, and forgot about the large sheets. So prior to the 1960s, what sizes were sheets printed in? Was a single letter sufficient to identify the position on the sheet?
And sometime soonish, the BEP will start transitioning to the new 50-subject sheets, and we'll have yet another system to get used to. I've heard that they'll use positions A1 through E10, across and down, but I don't know how reliable that information is. There are a few photos of a test run on the new equipment in this BEP financial report (.pdf).
