Japanese bubble glass cup

This cup is 3.5" long x 3" wide x 2" high and has its original label. It was sold to me as a sake cup, but it seems quite large for that purpose. It has a recessed pontil which appears to have been worked to smooth it. It is fairly heavy for its size but I do not have access to my scale, so cannot weigh it. It was on an online auction site for quite some time and I had made a couple of offers on it but they were declined. I finally repeated my lowest offer after several months and it was accepted. Calling it Japanese art glass as I am not yet certain what it is supposed to be.

The label says:

"Handmade
Oval Small Bowl
Foam"

Tea bowl? Dunno!