You can always put out a general post in random chat then if anyone is interested they can PM you for a private sale. If it's a Beatles related item then there is a Beatles Auction section but again it would be a privately arranged sale.
It is a discussion forum after all. Not sure a formal auction section can actually be set up on Pro Boards anyway.
Now HOLD ON just a minute!!! YOU HAVE ONE TOO???!!!
Friend: My favorite Beatles song is Band On The Run.
Me: It's not a Beatles song.
Friend: Wot! That guy, that guy, Paul McCartney sings it right?
Friend: Alright! That one is my favorite Beatle song.