Sz 14 (may fit 10-12)
NWT!! 90s Vintage Scott McClintock Black Velour Halter Gown with Crystals and Mesh Cutout Waist

Flat measurements:
18.25 bust
14.5 waist
21 hip
21.5 back slit
58" long from neck strap

Plenty of stretch

One of the sexiest styles from the 90s that has come right back in the past year or two - and this gown is brand spanking new with tags as well.
Plenty of stretch, maybe a little less so in the waist because I don't know how well the mesh would hold up to being seriously stretched. Back zip and 3 back buttons at the neck that I didn't bother fastening when I had it on the dress form, so if buttoning would bother you, probably not an issue. 21.5" back slit for movement.
I clipped the dress back on the dress form in the 1st photo but not in any of the others.

This item is sold from a vintage boutique in Cleveland, Ohio.