The functional and cosmetic differences of which I am aware are 1) EIs up to 3200, instead of just 2000, 2) shorter advance stroke, 3) shutter speed in viewfinder, 4) plastic-tipped advance lever, 5) advance lever does not stick out as far in the "standby" position, and 6) timer/MLU/DOF multi-function lever is now the same as the one on the F-1, skinny and black, with a white center line, instead of the fatter silver scalloped lever with no center line on the earlier models (carried over from their FL SLRs). Since it is roughly to the original FTb what the 1976 F-1 is to the 1971 F-1, there may be some minor internal changes as well.