I think there's a good chance that is Reichenbach R-88 Opal Violet.
http://www.glasscolor.com/products/d...cID=22&pID=459
If you go to the link, the page says "Purple Rose Special or Opal Violet."
Reichenbach now has a Purple Rose R-733. " Purple Rose, similar to Zimmermann's "Purple Rose Special"."
You can buy both in frit sizes up to 4.
Of course it's hard to tell from photos, so it might be Zimmermann. Here is a photo of Z-99.