a stunning piece Monica - designed to make an impression on your visitors, but sorry can't help with provenance or real date, but would comment on your thoughts about Egermann …………. I know little about the guy, other than believe he is remembered more for his invention of staining - both yellow and red - rather than full overlay, which believe is how you are describing the manufacture of the red colouring here.
His colours were apparently applied by brush and then lightly fired I think, which gave the effect of flashing, which was a more complex method of dipping a clear glass into a coloured glass to provide a layer of colour thicker than staining. Both staining and flashing provide a surface that can be wheel engraved or cut to reveal a clear glass design through the colour.
Are you sure your lamp is clear over ruby, and not the other way round - am sure you're right, but difficult to see in your pix.? Is the book example you show a known Egermann lamp?
So, on the basis of not being stained, then possibly not Egermann, but a great piece and a good buy.
