I don't know if he really knew those guys, but it wouldn't surprise me if he had met them. I think he was quite a bit younger than they were though.
He did know Elmer Keith somewhat and they sold guns to each other on occasion. We have a letter from EK regarding a Westley Richards double rifle he bought from my great uncle - he seemed well pleased with it. I know one of EK's many attributes was his prolific writing so there are probably thousands of letters from him around. I have heared that he always made great effort to respond to letters sent to him.

The Dubiel actually has "Barrelled by Griffin and Howe" on it, so I am thinking they didn't build it originally.
It did have a G&H sidemount at one time - as the old photos show. The old holes are now filled in.

The Newton he bought in a pawn shop here in Denver back in the thirties. It originally was owned by an attorney in Atlanta - how it ended up in a pawn shop I'll never know...I'll post some pictures of it in the classic rifles section.