It might be, but with a piece this small and with the button over the pontil scar, it might well be Monart, although I'm not overly happy about the way the green seems to be put in - it looks a little blobby to me and the clear backgound is unusual.
Hang around a while - somebody else who knows a lot more than I do will be along shortly to help you.

Whoops! cross-posting
and I read Vasart for Ysart in the title. Thanks, Gary for your vastly superior-to-my comments.
