|Betty Draper aka January Jones infamous corset, by Lady Marlene in their "Baby Doll" line.|
After following and keeping up with the trends on Mad Men, mostly the lingerie to see if they get it right (for the era's). They were spot on with this. Season one takes place between March and November 1960. This corset/bra/panty all in one, better known as Panty Bra-s'Lette by Lady Marlene and called "Baby Doll". The magazine ad is from 1959.
For a mere $2495, you can have one too, and it's the original, being offered for sale here, The Prop Store.