love those 60s ruffles! i must say though that in all the decades i have bought/sold vintage lingerie, i have never seen this kind of top. the ruffle front bra, yes but the back? or lack of it? i don't know how to measure it but i think you're safe if you are a cup size under a D. also, you could add a back closure by tying a piece of lace across the back. found two places where tags were removed so no help there.

panty measures 24 to 38 waist

This item is sold from a vintage boutique in Austin, TX.