idea that it is not framed. Are you sure about that? If you look at the back side of card board, are there tell-tell indicators of a frame? Perhaps a color differentiation along the edges, or maybe grooves from tacks or nails used to hold it inpalce?

I am not real familiar with such advertising items, but exposed glass edges just doesn't seem right ofr such an item.

With repect to re-glueing the item... If you just frame it, you won't have to glue it at all.

Jim