I was thinking not Mdina but quite possibly WMF.
I do have my "worm" plate, which for years i did beleive was Mdina, but Rocco told me was WMF (with catalogue number).
I've just got it out and the base is finished off in pretty much the same way as this is.
A matte base, with an irregullar shiney centre which seems to have "fingerprints" on it, but they're part of the glass.
It is also deeper than any other Mdina charger or wide bowl I've seen, as this piece seems to be.
Rocco said my worm plate dates to 1938.