Open Faced Sandwich – Oxymoron?

A hot turkey sandwich is accepted as a sandwich, although it is not technically correct. Is it not closer to Welsh Rarebit than to a sandwich? I suspect the turkey sandwich originated in closed construction and evolved into its current form, white bread (untoasted) topped with sliced turkey and slops of gravy.

Thomas Head has some interesting thoughts on the origin of the term “open faced”.

OPEN FACED
I couldn’t find a specific entry in the OED, but I think it’s likely formed from open meaning “uncovered”. “Open headed” or “open haired” mean with head uncovered. I don’t think it’s likely that it comes from open meaning honest or generous, as in open handed. On the other hand, it could come from cards–an open faced card has its face up.

Which reminds me of my favorite riddle.
Q: How are the Prince of Wales, a father gorilla and a bald head different?
A: The first one is an heir apparent, the second a hairy parent, and the third has no hair apparent.