Hi Jeremy, The strobe wheel you have with the hole is for the friction version of the Reference, this was brought out before the Hydraulic and was a means for fine adjust of the final drive speed, dad then updated this with the hydraulic and hence introduced the ball bearing. All that needs changing is the spindle that the strobe rotates on, i can send you one of these, just email me your address to info@transcriptors.net
Regards
Michael