What would this trade for? I have a friend who informed me that he has 2 bottles in his cellar and was thinking of trading the one with the messed up label. He loves gueuze and was looking for mass quantities of just regular cantillon and fonteinen. I wasn't sure but told him he's an ass for having 2 bottles.
The trade value is pretty high but that is going to be tempered by the fact that the beer is way way too old. You have to find someone willing to pay the price that doesn't actually care that the beer is over the hill and oxidized.
I think there are plenty of people wanting to tick it that 5+ Cantillon would be an easy starting point.