This is a rare post card, indeed. Including post card collectors and PCL collectorsthere are at least six known copies. I purchased my copy (SGC Graded 40) in a private transaction. Two months later a similar (but not graded card) was sold by REA. Since that time, including the card mentioned in this post, I have seen two additional examples.
I would urge the owner to have the post card graded. If grades it 70 or above, it should bring at least $2,500.
By the way, if you have further interest, look at a copy of the PCL memorabilia program which cataloged a wealth of the PCL material the San Francisco airport.
To ensure the best price, I would suggest auctioning the item in REA's Fall 2013 auction. If you do so, REA will have it graded. Very few of the remaining important auction houses truly understand the rarity, value and market for baseball postcards The other knowledgeable sources are Lew Lipset (no longer in baseball auctions) are Doug Allen andRon Oser
Good luck
Bruce Dorskind
America's Toughest Want List
bdorskind@dorskindgroup.com