I can understand Frank's reservations, but I have to say whether the mark is right, or wrong, this IS a piece of Gray-Stan in a known and recorded shape. See Parkington Part I, 16 October 1997 lot 373 for a yellow and orange example.
As for the signature, they vary greatly, but can generally be split into two versions, both being produced by use of an engraving tool (wheel? or diamond?). One is small and neat, the other larger and looser in interpretation. Naturally, they vary individually.