"Melon Balls" are one color in my experience at least.
There should be some sort of "Pontil" included.
This one appears to be machine made and if I had to guess on the maker it would be Master.
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There is no AV here that I can see.
These used to be called Akro "Experimentals"--this one is a dug Akro imho.
The cutlines line up with what I think.
I appreciate all opinions and hope to see some more.
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This is a classic example of a veneered marble.
Notice the white that shows in the cutlines.
If you were to break this one open it would be all white inside.
I think that @Melissa has some input to share here.
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Vitro Oxblood is a bit weird--if it were mine--I would call it ox for sure.
Of course, I appreciate all opinions and hope to see some more.
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Al and Ric are right one with this one.
It is a nice find and a great ask--a keeper--these are quite old and getting harder and harder to find.
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The clearity of the glass makes me push towards a USA made classic of some sort.
It has big bubbles though and one not quite finished cutmark--kinda ruff really.
If the second image on the left if a cut-line along with the third image on the left--a slight "V"--Vitro--no name.
Nice find--no better ID from me at least.
@Ric is right on again.
Marble--On!!