One TB had the stock encoder wheels, and one had the GGG upgrades. Reference: I used a pair of brand new 3' Happ 'Golden Tee' AKA 'High Lip' trackballs, interfaced through an OptiWiz. I wondered, why not Happ? Betson and Happ TBs both appear to use the exact same diameter optic wheels, with the same number of holes, so it ough to be no problem. The Groovy Game Gear web site lists their trackball booster kits as being compatible with Betson/Imperial trackballs.
