Michael,
I can see why the Kamei suggestion was made, and I know that Anita has seen far more of these than I have, but I have some reservations. I've had a a couple of Kamei and they've both had three indentations in the lip. The appearance of the ashtray is almost square, unlike your piece. And I agree with you that the Kamei pieces are thinner-walled than this piece.
Also, like Wayne, I've never seen a Kamei piece with bubbles. Of course, it may be that I wouldn't recognize a piece with bubbles as Kamei, so that's not a strong argument.
I wouldn't suggest Murano as an alternative. The form of the bubbles (small bubbles behind a thinner layer of elongated bubbles) I tend to associate with Chinese glass.
An interesting research project again, Michael.
David