Long 1960s dress

13in waist laying flat. I am regularly a size 4 and the dress fits like a glove. I think it would fit a size 6 best because I have my H cup boobs crammed in this dress. no damage but it will need the zipper replaced. it is a 22in long zipper that runs down the back. no stains or tears. just separating from the zipper and it looks like it has just happened over time.