The bottom part will just be what is called surface decorated.
The hot gather of glass will have been rolled over the small coloured pieces of enamel which would have been laid out on the marver, to pick them up. You will end up with a surface texture exactly as you describe, just as long as they are not fully rolled into the gather, or futher cased.
I'm very green here. I'm completely in love with it, and very glad it's owned by somebody who appreciates it so much. But finding the maker would be the icing on the cake!