I would say it is a misses size large. I think the main thing is that it would look best on someone who doesn't wear over a C cup bra. If you are large busted it wouldn't fit right.
I can't seem to find a label but feels like a cotton and poly blend and very soft with the design airbrushed on the material. Although the material is lightweight I wouldn't describe it as see through but it kind of depends on the person wearing it. I didn't feel the need to wear anything underneath as long as your bra is white or beige. Good luck if you bid:)