Cincinatti double decker?

[AAllan at AOL.COM]

Another dish that seems popular in Cincinnati goes by the name "double
decker." It's a sandwich, presumably with a third slice of bread; but some
Cincinnati websites list it without further description, so I imagine there's
a standard unmarked set of ingredients.

Sometimes it seems the equivalent of what others call a "club sandwich," but
sometimes not.

I wonder if some Cincinnatians could explain it, and whether there are
"double deckers" anywhere else.

- Allan Metcalf