Bought belt pulley assembly thinking they were for my Thirty but not exactly sure what I have. Both look like the same mounting pattern but one drives to the left and one to the right. Also what is supposed to be mounted on top of them?  Thanks, Mike 

Tailseat mounting bracket, I also think it is possible to change pully and shaft etc to the other side.

Wombat

Both are for the S/PS Thirty. The one with the cast iron pulley is older than the other one. The bracket on top of the one with the paper pulley is to attach the seat on orchard tractors. Just think of a pulley spinning below your bottom and your leg bumping into it all of the time with the older one.

Thanks for the info, so these are for tailseat Thirty’s? Or do all thirty belt pulley have mount for optional seat? The early version would have been turning all of the time and the later one could be disengaged with the lever on the rear? Approximately what year would the early one be correct for? Thanks, Mike

The early version with casting number 420 is correct for a Best 30 and there where Tailseats. Have one on a1923 Best 30. A few years later, they would’ve changed to the other style with the shift lever, and you can takeoff the seat bracket to use on a top seat.  Skinner 

The bracket on the later pulley came as part of the assembly when the pulley was bought. It is part # 1A2254 in the middle of the parts diagram. The early pulley was a Best design  but it is perfectly good for a top-seat tractor through serial numbers S10173 and PS11973. All Thirtys up to S4682 were rear-seat tractors.  Either one is perfectly fine for your tractor, pick one put it on, and enjoy it.  There is a serial number split at S10174 and PS11974 that would require a different shaft between the pulley assembly and the upper transmission shaft on the late pulleys, part numbers 1B2426 and 1B2425 changed at those serial numbers.  Someone at some time used the seat bracket on one of my early pulleys as a drawbar hook and broke it off of the housing and then brazed it back on.  It ripped quite a chunk out of the gear case.      

Great, thanks for the info. My tractor is a ‘28 top seat wide gauge so I should be good. Just started second guessing the application for them after they were dug out and at my place and I could look at them closer. I believe the newer style one does have a different size coupler with it that may go to the newer tractors. Either way one of them should be able to fit mine. Probably won’t install it until I want to use it but always seems like a good idea to pick up parts and accessories when you find them. Thanks again, Mike

I have a complete PTO attachment for a 30 would bolt right on.
If you would want to trade for the early belt pulley attachment. Skinner

That sounds interesting, where are you located?