One of the shops in the Burlington Arcade used to make formal versions of these. They worked great and looked pretty cool. The fronts looked like a regular waistcoat with tabs as in the photo above. The back was like a regular pair of brace buttons and went under the waistcoat back (which was itself a relatively low back typical of a backless waistcoat). I remember it pretty well, having borrowed a pair. I haven't seen them made in many years, though.
2/24/15 at 2:27pm