My PTO shaft stopped an inch short

[RoyJackson]

Not the OP but I would love the part number. We have an old rotary cutter at the farm that someone cut the driveshaft. The extension would work perfectly. Thanks!

This is exactly what you want:
PTO ADAPTER 1-3/8X6SPL M. X 1-3/8X6SPL F - Agri Supply

BTW, I have read (on TBN, I think) that use of these extenders/adapters can accelerate wear on the tractor's PTO stub shaft bearings. I use my extender for a chipper and it comes off when I'm done with the chipper. So, a heads up...but again, I just read it and have no idea if what I read is valid concern.