Stephen, I think your crease is a cold roll.
What kind of marbles did that one come with? This Vacor is my only specific guess. If it's not this, I'll sit back and wait for someone else's ideas. https://www.billes-en-tete.com/detail.php?id=211
Is that sunlight filtering through? It's artistic but it's throwing me.
Can we have a view in different light of that seam that's peeking out on the bottom left view?
Miller swirl is sort of a dicey category.
Luckily, these happen to be Peltier Multicolor Rainbos. (Some might call them Multicolor Swirls.) They are from the 1930's.
At least the left and bottom one are. I think probably the right one also but another view could nail it down.