It looks like a 1959
California built 24' Tradewind, very close to 24T-0114 whose hot link is on the bottom right of the Vintage Airstream photo page linked below.
Ask the seller to look on the small data plate just forward of the door handle and read the numbers stamped into that plate. Those numbers should be the serial number, and the trailer model can then be identified by its serial number on the Vintage Airstream photo site here:
1959 Trade Wind 24' - Vintage Airstream
The seller also might find on the next lower line the month and year of manufacture stamped in the serial number plate. Good luck!