Isle of Wight Studio Glass was pretty much a family business - Elizabeth did have considerable artistic input, although not when they were at Mdina - she was too busy trying to raise their children then, as they were quite young.
It's the tool used to write the name that concerns me. Normally, Michael Harris would use a diamond engraver - but this looks done with a vibrating sort of tool. The difference in tool might account for the different look of the writing, as the letters are thicker.
This isn't normally the sort of piece that would be signed. Meadow Garden was a "bread and butter" sort of range, so perhpas it was originally purchesed at the studio and the buyer asked for it to be signed and only a vibrating tool was available?
I'd be interested in Glassobsessed's opinion. He's better at signatures than I am.
I'm pleased to hear you did not fork out a large extra amount of cash for the sake of some scribbles on the bottom.
(I'm a bit of an oddity - I don't personally rate a signature as adding any value, just to the cost. )