Thanks guys. Sorry for being lazy before I asked.
I was mostly interested in size and didn't think I would find that, so I tossed the rest of the questions up there as an afterthought.
Here's a first run pic from one of the threads Mike mentioned:
In one of the other threads, Rick mentions shooter size marbles in his first run set but says they could just be fillers -- bananas -- not filamented.
So ... about 2000 marbles in the first run and about 5000 marbles in the second run?
So, there aren't many available to find "in the wild".
(I saw a large-sized marble somewhere which made me think of these 1st and 2nd runs ... but I didn't know if it was worth mentioning these runs as a possibility ... afraid to confuse the matter. And now I see odds would suggest that was a good decision.)