early PDP-11/45 info sought

My KB11-A prints have an 'overall' date of "4/76" (on the front page), but prints within the set seem to be older. E.g. my M8100 prints are dated 2/72, and none contain any entries in the 'Revisions' block (lower left). However, they are marked as Rev. D, which is newer than the KB11-A prints at Bitsaver, which are marked as Rev. C. So I have no idea what changed to cause the rev update! (The first drawing, the board layout, does show a listing for 'D', so maybe it was just a layout change?) The boards aren't all the same rev, though: the M8102 in mine are marked Rev. C. My KT11-D prints are dated "5/72" (on the front page), and the M8107 prints are hand-marked as Rev. A, but the M8108 pages have mostly been replaced with 'yellow-sheet' updates with Rev. F, dated 6-'73. Noel