"A Field Service Modification Work Order was issued on 21 Jan. 1943 instructing that all rifles currently in service were to be changed to the new configuration." ( the long pinion Type 2) This would seem explain the "knurled elevation knob".
That's great information, thank you. I guess if I read the book, rather than just looking at the pictures, it might help with my overall understanding. I'll have to see if I can access the pinion without goobering anything up and check for a long or short pinion. I've done it on an M1Aicon, but never on a lock bar rear sight.