DG Ware England glass lidded jar

Here is a really interesting & unusual small lidded jar that I found in a local op shop today.
In all my years of collecting glass I've never seen anything like it.
The jar seems to be made from a thick outer layer of clear glass with a "sandwich" effect that appears to be painted inside. Even the label on the base is actually embedded in the clear outer layer of glass. Inside, the jar is lined in a cream/ivory colour which I suspect is a kind of glaze or even paint. Curious indeed!
The lid is silver plate, marked EPNS on the inside.
The embedded label reads English Make D G Ware Patent No. 103700.
From what I've been able to find out, it was a product of the Decorative Glass Company, Stourbridge, founded by A H Guest, circa 1920s - 1930s. They made items with enamel designs or transfer prints sandwiched between glass.