ID help please? Stamped Evan?

Hello folks,
I found this vase the other day and I have been trying to decipher the stamp on the side of it but with no success. I am sure that someone out there will be able to point me in the right direction. It measures 13.4cm high by 14.3cm side to side.
The vase is quite distinctive but unless you know where to search, there are too many to scan through.
Many thanks in advance for any help.

Stamped Evan, I think.
Mark Griffiths has used this bright green glaze; not many potters who can do it as well as this