Welcome to our forum.
PS...You don't think it could be buckshot, do you?
Chris H nailed it, they are the ball bearings from the rotary jets. About 3-4 times/year we have a customer come in needing a new jet. We just give them a new one to pop in. Easy as pie.CEO
No, BUT when we were digging out the concrete slab for the tub, I did find a few spent shotgun cartridges!-Ed