Sorry for the delay--as with most things, life gets in the way!
Anyway, these are the best I can do without taking it out of the frame and scanning it (which I'm not opposed to doing, if necessary). I've been searching and searching, but have had no direct hits yet. Thanks again with your help on this, I am excited to get to the bottom of this mystery!
...I've also added a few detail views of the various parts of the piece. Hope this helps!!