If you come across a vintage guitar look for the serial number
. Surf the web and find out what serial numbers that was used in those old times and check if those guitars you discover has a satisfactory figure. Do not hesitate to obtain if the charge is realistic. Using some skill gained over time you will promptly understand if an aged guitar is worth purchasing or not.
A excellent location to begin exploring forvintage guitars would be on-line and I propose Ebay, where both sellers and ordinary people sell guitars.