I have it on very good authority that Rogers was contracted to provide Buddy with two kits per year, but that he rarely took both sets. Perhaps that is why we rarely see a BR Rogers kit around. I can't speak to the other companies and endorsers.
Through my teacher Phil Stanger, who was good friends with Barrett Deems, had said similar to me once about Slingerland drums, that an endorser was only supposed to get just two sets a year. I imagine the drum companies wanted their endorsers to always have the lastest, and greatest they had to offer back then.
And although I have never had personal dealings with Barrett, or was ever close to him like Phil was, it sounded like he also played games with the sets according to Phil, either giving them away, or selling them outright.
Thus, Barrett, like perhaps so many other pros were constantly at odds with drum companies over their contractual agreements.
Phil as well was a Sonor Endorser back in the 60's, but I don't ever recall Phil being able to pull such with Sonor. Mark