It looks absolutely right to me!
I agree completely it's Michael Harris' script, not Tim's, I've just checked both.
Normal artist signed pieces have the full artist's name, and Isle of Wight England, but the plain Studio name engraved either as "IoW Glass, England" or "IoW England" without an artist's signature can signify a piece which was bought from the studio archives.
I can't check archive pieces sold while Michael was still with us - I have only two - and they're marked by Tim, I believe.
The designs produced at Kerry were based on designs first made at IoWSG - it can be hard to tell which is which - unless it is otherwise marked with IoW, or if it's one of the later Kerry ones with the flame mark reversed.
But there really is no way of telling IoW from Kerry otherwise.
And yes, they were both making this design at about the same time.
IoWSG means Isle of Wight Studio Glass. IoW alone could refer to Alum Bay, or to Glory Art Glass as well.