Considering the place (along the canal), the small shop, the technique (engraver), I suspect that your man is Luigi Camozzo.
I have chatted with him just one time, due to I work with other coldworkers (Ferro family), and probably he doesn't know me, but I know that he works very very well.
This the address:
Fond.ta Venier 3 Murano (close the big iron bridge) phone 041-736875
I hope these infos can help you
Sincerely
Alex
www.artofvenice.com