What is this? Small tray, millefiori glass over metal?

I purchased this interesting tray at an estate sale. It is 9” x 6”. It has a chip on the back side. It looks like glass over metal. The top of the tray has lumps of color that protrude up to 3/8”. There is also millefiori cane worked dispersed among the lumps. It is an unusual piece.

Does anyone know what is or where it could have come from? When could it have been made? It is intended to be a display piece or was it meant to be functional. Any information is greatly appreciated!