I imported an Italian smallframe a few years ago and was able to get a certificate to prove its age, for DVLA purposes, through the Vintage Motor Scooter Club
http://www.vmsc.co.uk/_pages/registrations.htm It does require you to provide the frame number though. However if you can't see all of it, it's sometimes easy to guesstimate what it is, since there weren't a huge range of prefixes. There's a website here to help you
http://www.scooterhelp.com/serial/ves.frame.serial.numbers.html If you know the model and approx year of manufacture you can possibly work it out. Failing that, if you find the engine number you might be able to cross-refer it to a frame number; assuming its still the original engine.