Could be 'Black Futura Gold Edge'. Their could be other names for the same plant from different nurseries. Here is a link to check;
http://mrec.ifas.ufl.edu/foliage/folnotes/sansevie.htm
This is only a guess, very hard to ID with just a picture. Here's some of mine.
Stush

Thank you Stush,

Based on comparison with your photo, the information on the link, and the fact that my plant has 7 leaves on the one rosette, I am hopeful that it is Black Futura 'Goldedge' as you suggest it might be. Of course, as you say, an ID from a photo (and not the greatest one ever) is always a long shot, but some of the evidence at least points that way.

There were some variegated trifasciatas in adjacent pots in the store. They were of similar height, but all of them had much narrower leaves than this one.