Phoenicia glass is an offshoot of Mdina, it was set up by Leonard Mulligan, at Sliema on Manoel Island.
Leonard Mulligan was also one of the business partners Michael Harris had when setting up Gozo Glass a few years later, in '89.
I think this thicker script is produced in a quite similar manner to the thicker Mdina scripts - a vibrating drill thing which goes sideways.
I've never seen the thick script before on a Phoenician piece. I don't know much about what's early or late. Some pieces are variations of a theme from Mdina, very well executed, what I believe to be more recent pieces are quite different - and very sophisticated indeed.