Since there is no other response, I'll stick my head over the parapet.
I don't think I have ever seen this label (I see many hundreds every week).
IMHO It could be
a)very recently introduced by a small factory that has not yet reached the secondary market, or
b) it could come from somewhere other than Murano. ,or
c) it could have been added after wholesale by a retailer, and unrecorded hithertoe