Gorgeous marbles, Ron.
That's an interesting question, Dan. I think you can find swirls which are practically twins ... and companies could have distinctive traits like the shepherd's hook of a Cairo Novelty. I had a group of swirls where the ribbons looked like they formed flowers. But was there anything deliberate about it of just what happened sometimes when a stream of glass a certain width fell a certain height?
Controlling it to be exact matches? I don't think so.