Red Slag UV Glowers

[Spherophile]

The swirl in these large slags glows very brightly under UV. They measure around .94” and look machine made, although I see some flaws (one is slightly flat on one part, another has a slight fold). 
 

 

[Steph]

With this view and that size, I'm gonna suggest Jabo.

[wvrons]

Jabo swirls. Not slags. 

[Spherophile]

I had to look up the difference between a swirl and a slag, but I couldn’t find a consensus. The most common characteristic seemed to be that only older marbles are slags. Some made the claim that slag was never a name used by the manufacturers (slag being a term reserved for waste glass). 
 

Either way, Jabo apparently only made swirl marbles, and I guess that’s what’s these are. 
 

 

[Steph]

Right about the name slag.  The typical manufacturer term for slags was "onyx".

 

"Onyx" became a problematic name in the early 30's if I recall correctly -- because the true  mineral onyx industry was trying to get protections against glass makers presenting their products  as onyx -- but by then marble makers were mostly switched over to non-slags.   Hmmm ... now I start an argument in my head about how Akro continued to use the name "onyx" into its corkscrew-making days well into the 1930's ... but I refuse to delete because most of what I said above is still true ... I think.  lol

The defendant in the FTC case was  Gropper and the order to be very clear about what was meant by "onyx" applied to the Peltier marbles which  Gropper was selling.  

https://books.google.com/books?id=y17ilneaDCAC&pg=PA274