It's a label that's seen quite a lot on pieces that are very difficult to attribute to any one maker. For example, I've got it on about 4 or 5 pieces that vary quite widely in style and execution. It was suggested to me once that the best of my bunch was made by Campanella. I've wondered if this was an early version of the promovetro label, i.e. a label used by a number of companies. That's still wild conjecture. There's been a fair bit of discussion on the board about this label, if I remember correctly.
Your piece is toward the high end of the range of pieces on which I've seen the label, but that may be my taste.