Are the balls you are finding all standard pinball size? Do they all match?
I find normal pinballs pretty mesmerizing with the spherical chrome but what you are describing is definitely something different. I'm wondering if this might match with the report of a machine having different sized balls.
2 days ago (+1)
Internet says a standard pinball size is 27 mm. These seem about 30 even, but I could be measuring them wrong? I don't have calipers so I'm just using a normal ruler. I will say the finish seems a bit weird -- I don't have any standard pinballs around for reference, but I checked my reflection in a ball bearing I had and it's not spiraling the same way.