A friend of a friend has a complete set of U.S. patent books from 1912 to somewhere in the 70's. He's moving and is reluctantly parting with them for about $15 apiece. If there's any particular book which you want for patents on marble machines or anything else, let me know soon so I can get you in contact before the movers arrive.
A cutline is more or less the same as a seam. On some marbles people are more likely to say cutline (marbles such as MFCs). And sometimes I say one or the other without thinking why.
I don't what to make of that cutline. Is it the only one visible?
Nothing about it particularly said Vacor to me ... but since I didn't recognize it as anything else, I went to my favorite Vacor page.
So, this is my guess. https://www.billes-en-tete.com/detail.php?id=119