http://www.ebay.com/itm/271465688959
This vintage swimsuit was made by Jantzen and was sold in Brooklyn, New York by the Schwartz Mens Shop. It is the “Half Hitch” model, produced from 1936-1942, recognizable by its tunneled buttonhole belt loop arrangement, narrow belt with hammered look buckle and side piping.

Waist (unstretched): 15″ (doubled =30″)
Waist (stretched): 18″ (doubled =36″)
Side Seam: 9″
Rise: 11-1/2″