I got a generic pto (reg shaft) one at auction without a manual. Mine is part for part like one of these Worksaver models.
I see they have a different model with a flex shaft drive of some sort - like yours?
Anyhow, I found a manual on their site for mine. They offer a parts list & on-line manual. No idea if it is the same, but page 9 of the manual has a seed rate chart - might help?