@Jamiebull13,  I'm not able to post comments on pictures in the gallery.   So hopefully you'll see this comment here.    
	You wrote, "Is this a rare vintage piece? I found it in central Arkansas while hunting for arrowheads. Any info would be much appreciated."    
	The answer is no, not rare.  Grooves like that are called "cold rolls".   That's when the molten glass glob which turns into a marble wasn't quite hot enough when it came out of the furnace.  So it wasn't about to smooth out completely as it went down the rollers.  
 
	 
 
	 
 
	 
 
	Side note: 
 
	@bumblebee, I tried to link Jamie's picture into this thread, but as has happened before, when I tried to link to an image in the gallery I couldn't post the thread at all.  I had to start a new thread and retype the text without the link to the gallery before this would go through.