you might email the guy who runs boxcameras.com
and ask him what he thinks it is. he's a nice guy ...
it sounds from your research it probably is a poco but who know...
there weren't a ton of cameras with a variable shutter speed mechanism
i had a falling plate camera once with one, it was something-else!
the delmar is pretty simple, and looks like the cyclone
just a push on the side to trigger the shutter and
a 2 position dial on the front ... milk glass on the top and side
... and a back end just like yours for storage and the clips
for the holders.
i used to use a polaroid 545 back in mine too
john