Rare 1970s red yellow blue collared sleeveless button up tank top size 12 fits 8

Rare 1970s red yellow blue collared sleeveless button up tank top tagged 100% cotton machine washable made in Japan size 12. Tunic length with front slit. I am typically 10-12 in vintage sizing and I could squeeze into this but highly recommend to an 8 please refer to measurements it has no stretch also feels new. Buttons to a cropped and has slit opening from around belly button down would be great with high waisted jeans. Waist-16in Length-29in Pit to pit-18in