Well, the complicated matter of all this is that there are some so-called low beat 21600bph A7750's that have the same pinions of the highbeat 28800bph A7750's. Not all are created equal, but rather from whatever parts are available I'd imagine. You just won't know which you have until you try fitting the hands on the Swiss ETA.
The long and short of it all is- No matter which you have, Zig can modify the hands to fit a Swiss 7750 if it's necessary. He did it on my 3717 when I swapped out to Swiss.