of course you can bring your duplicate banknotes to the bourse!
First of all, some dealers (not all however) will accept your duplicate notes or (part of) your collection you want to sell, in trade for notes from his or her stock!
Secondly you can offer your duplicate notes to a fellow collector in the restaurant area. You may sit down and trade there, but this is only allowed between collectors!
HOWEVER: we will not allow backpacks, suitcases or briefcases stuffed with notes (read: commercial activities) in the Restaurant - or elsewhere in the building - if you have no table! So, no commercial activities in the entire building = if you have no table booked = apart from the halls where the bourse takes place! The security people will keep an eye on this.
Bring your "mystery-notes" too
Everybody has one of more notes he cannot identify, don't hesitate to bring them. You will be surrounded by knowledgeable people! Ask for assistance at the Reception Desk.