have you searched through old bechers to see if that design around the rim has been replicated anywhere?
I have seen that design somewhere. It might give you a steer on the time frame or possible maker.
Also how are you sure not Egermann?
And what years do you think this bowl was made? Is it possibly 1920s or 30s? it has that look with the shape of the bowl and the faceted short cuts?
How big is the bowl?
Is it thick heavy glass
Is the rim cut, polished and then bevelled on both edges?
Is there a polished pontil mark on the base or was it ground and polished flat and then engraved?
Have you considered looking at Lobmeyr, or Riedel?
Also, sometimes it takes years to get an identification

and then all of a sudden you see a matching piece pop up on the board or someone finds yours when looking for theirs and manages to get an identification.
That's just how it is with unmarked glass. Millions and millions of pieces were made.
Sorry I can't be more helpful, but hopefully with a bit of brain storming a clue might emerge

Edited to add : I have seen that design around the rim (or very similar) on Lobmeyr glass. However I'm not sure how useful that will be, but it might lead onto other things.
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