What Ric, Kimbernugs and Melissa said X2.
There was a drop in coloration when the Master Marble Company became the Master Glass Company.
It was all a matter of keeping up with the new import rules regarding the Japenese and other Asian countries after WW2. American glass companies could hardley keep up with the changes and prices. I have always believed that yours are pre-war and the brushed patches are after-war. Quite a drop in eye appeal imho.
Great marbles!
Marble--On!!