Hello,
I am not sure if you have already addressed it. From my research I have found that a Mesu-mk1 usually has 1:2000 gear ratios (I think I have heard also of some examples with a 1:2800 ratio). The encoders at least in mine are 4,000 steps in the RA (HEDM-5500-B02) and 2,000 steps in the DEC (HEDS-5540-A02), for a total of around 8,000,000 and 4,000,000 ticks in the RA / DEC resp. Notice that for the encoders we use the CPR which is 4xPPR.
My second-hand mesu-200 which came with Argonavis/servocat has been converted to OnStepX (it still needs some fine-tuning though). Right now OnStepX is configured for 22229 ticks/degree and 11111 ticks/degree in the RA/DEC resp.