I'll buy the asterisk-shaped ring idea but why was only one out of 6 made that way? Parts store substituted one when the engine was rebuilt in the past and they had 5 of another design they wanted to remove from inventory? I don't think it would be a balance thing. That doesn't make sense to me, anyway. One checks/confirms/adjusts weight after the piston is made. Maybe if the original poster could show us an image of one of the other pistons we might be able to see if we think it was the same mfgr. If it was the same maker, then we might have a trail to follow. If the other 5 were made differently it might argue the maker was different and if so there's a large clue to the answer.
