I have a vintage Nishiki Riviera GT frame with some dents on the chain stays (see pictures). I think the dents are deliberate (they are very uniform), the one on the right is probably for chainring clearance. I've been planning on building it up for some loaded touring (a week or two this summer).

Do any of you Nishiki experts know if this was a standard thing for these frames? Or could it be that the dents were put in later for wheel/chainring clearance?