The standard 7750 movement has the chronograph/ stop-watch function. It has 3 subdials at the 12, 9 and 6 o'clock position. In the standard 7750 movement, the second hand (small seconds) is at the 6 o'clock sub-dial. Whereas I believe (experts, corrent me if I'm wrong), the gen AP ROO has it's second hand at the 12 o'clock position.
Since most of the AP ROO reps use the standard asian 7750, the second hand subdial is in the wrong location (it is at 6 o'clock, when it SHOULD be at 12 o'clock). So, for further accuracy to the gen layout, you'll need to have this modified.