I am seeking info too. I assumed mine was an early Powerbloc until I took it apart today and found Eastern industries stamped into it. It works on same principle as Powerbloc. The little screw in caps that hold the weights inside the sliding plastic blocks were brittle and shattered when I tried to take them out. Interestingly, the powerbloc cap threaded in. Aside from that, there was no interchangeability with other Powerbloc parts I have. I wonder if this was a forerunner or competitor to Powerbloc as they were both manufactured in Drummondville Quebec? Mine is for a 3/4" threaded shaft, I assume early skidoo, but could be others.Can anyone tell me anything about this clutch ? Is it any good ,Has anyone ever used one and what machine does it come from.