Brent Marshall gave these to my nephew. A couple of years ago, he passed them on to the person he knew would love them best. I feel lucky to have them, along with one of the best nephews in the world!
My understanding is that Mr. Marshall does not make marbles often. Although, you can see the influence of early marble makers in some of his work.
The big one is about 1 13/16" . . .
Cheers!