It looked like loopy handwriting. The tool used was
very fine, although there was evidence of it leaving the surface during the creation of the lines... they were not completely smooth. It looked hand-done, by somebody very experienced.
It was on every glass, and exactly the same. The script wasn't thick and "drilled" looking like the one you show. I would think it was a diamond point pen used.
The label was black with a gold outline and gold writing, it read Royal Brierley, it was a paralleogram shape, with rounded corners, much wider than it was tall.
The glasses themselves were of no remarkable cut.
NB.! I'm a philistine about cut stuff. It all looks pretty much the same to me, especially when it's standard classical patterns.
I did swither, for the sake of the mark, but could not justify having to buy the
whole set and Michael was hovering nearby, in a sort of; "Don't you
dare bring any more glass home." manner.

The letters were quite big - maybe 3-4mm, not counting the height of the capitals or the ls or the loops of the ys.
I did spend some time studying it - (as Michael got more and more grumpy and concerned about them appearing in the house.)