I live in California. As anyone involved in the vintage vehicle world knows, there is a sort of aura about old cars and motorcycles that have lived their whole life here in the state. It means they have never seen road salt, harsh weather, and have generally not been bitten too deeply by the rust monster. Sure, you see the rust-buckets out here, but honestly, most 50's and 60's cars from the East Coast have returned their ferrous metals to the mother earth by now. For us in California, one sure method of provenance used to be that the vehicle had its original old style black (or yellow) plate. Things are changing now, and one can now register any 60's vehicle with the black plate. So that will be less and less of a factor in determining where the vehicle came from... however people are always looking for that extra detail in their special vintage scooter, motorcycle, or car.
On the scooter side of the world, as with almost all of the vintage vehicle scene, there is a swing away from overdone restorations, and a value on originality. Even with some imperfections - what those on the concourse call "patina" - there is more intrinsic value these days from a collector standpoint in a totally original finish. One clear hallmark of originality on a scooter is the "running in" sticker.
The running in sticker was pasted on the inside of the legshields on Vespas and Lambrettas by the factory. It gave the new owner clear information on the correct way to take care of the motor in its first few hundred miles. Thirty years ago, the oils were just not all that great, and great care had to be taken with a fresh motor to avoid damaging it when all of the machining was still tight.
Though generally water transfer stickers, these running in decals seemed to really last. Just about any 60's scooter with original paint will still have a remnant of the sticker in place. I'm not sure if Innocenti ever stopped putting the stickers on the Lambrettas, but Piaggio seems to have stopped around the mid-70's.
Check out some photos of the original stickers:
From a mid-70's Lambretta Jet 200
From a restored Lambretta LI 150 Series I - this sticker is a reproduction.
This last one is from a 1971 Vespa Rally 180.