The seller cannot vouch for the operational condition, it is untested. 50% chance it can be used right away, but figure in $150 for a CLA and minor repair. With a 50year old camera, it's always nice to buy from someone that has tested it and knows what they aredoing.
For example: is the RF patch dim, aligned, shutter operating, curtains burned through? Without the facts, assume you are buying a camera that needs servicing. That is the way of EBay. This seller has great feedback, but does not deal in cameras. He likes like an Ebay "broker".
If it stays under $400, worth the risk. Otherwise, buy one that has been tested.