OOOH NICE! Several companies have used this type of technique:
* Daum developed it - but if it doesn't say so, then it isn't.
* Peill & Pützler had it in production in the sixties/ seventies as Schleiergraphit - check for a vague P on the side or on the underside. If it is P&P, designer is most likely Karl Wiedman, who worked at WMF in the 30s and at Daum "during the second half of the fourties" (go figure).
* Schott Zwiesel had several models in production in the seventies designed by Gangkofner - no marks there,
* And finally, Bengt Orup used oxide inclusions at Johansfors circa 1967.
Multiple choice it seems.