Iām sure Herman made marbles/spheres and that is how Jack got to know him.
Most glass workers are very open to working with enthusiastic people. Herman probably opened his shop and experience to Jack.
Personally, I have offered people a chance to make marbles on my machines. It is super fun for both parties. I get to relive the early moments of my discoveries. They get to experience mayhem.
The techniques that I see in your marble are classic hot shop techniques. The rough pontil finishing is an early example in the progression of refinement.
You state that he made ābowls and suchā. Well, marbles, spheres and paperweights fall into the āsuchā category.
If you believe it was made by someone else, then I hope you find the maker.
Sincerely,
John