Novice though I am on signatures, I found this in 'Italian Glass, Murano:Milan 1930-1970
To my inexperienced eye there are several similarities with the flow of the signature and style of writing looking correct. The text underneath reads; "Diamond-point engraved signature, 1960s-1970s", so it would appear to fit.Edit:
Just one area of concern, the up-stroke from the 'i' to the 'n' does not look quite right, but signatures always modify over age so the examples given (Anne's link also shows very close similarities to the one in the book) might not be truly representative. But given that the dish was sold without being attributed properly, it does suggest genuine.