In the 70's Labino played around with a glass formula that he got from Corning that would change color after it was made when exposed to the right type of light. you would put a mask on the glass and expose it and where the mask was it would remain clear and the exposed places would turn a reddish purple. There were several others that played around with this formula about that same time and there are some samples of it in the Corning Museum.
I don't think is one of those pieces though and if it was blown, cut and then encased as a graal piece, it should show some tiny bubbles that were trapped where the cutting was done. It's difficult to do graal and not get at least a tiny bubble somewhere.
It may have also been done using a technique called an "aussie rollup" where the decoration is fused on a flat sheet then heated in an oven and picked up on a hot gather and formed around it. Then it is gathered over in clear and blown out to whatever shape you desire. I think that technique has only been used for about 20 years though. It supposedly originated in Australia, hence it is called an aussie rollup.
Or it may be totally something else. but after reading the posts again, the tiny bubbles strongly suggest an early graal piece.