Well, it is not a slag, we can all agree on that.
I see two different types of white, one may be opalescent.
Lots of bubbles---no AV.
It is a big marble.
The cut-lines could be Peltier, or other.
I do not think it is an Akro or a Master made marble. I would not call it a Vitro.
It appears to be a vintage USA marble---hmmm--
My instincts say MK, but it seems kinda of big for that.
It could be a Pelt.(pass me some popcorn too)
Chime in Peltheads!!
Marble—On!!