There is no head gasket on a Piaggio (Vespa) Ciao. I was confused when I first removed mine, but a look at p. 17 of the Haynes shop manual clears it up: "The cylinder head can now be lifted off, noting that no head gasket is fitted."
I have two Ciao's (a 74 and a 76). Contact me off list (just respond to this post and I'll be eMailed the message) and I'll send you the serial numbers. Perhaps they will help?