From what I can recall off the top of my head, that was the 1000 series of pipe cultivators. The exact model number depended on configurations. I have a manual somewhere here on those, I'll have to look for it. I do know the same basic cultivator mounted on an HG/OC-3 was called the QD-895.

I'm thinking that there was no mention of it being the rare early style pulley saved you some money. Amazing what the right words can do to the price. I haven't done much more than take mine out of the box and check it out. Still working on other projects....