1. the dagger is fake and the whole "court circus" starts.
2. the dagger is good ,and Mongo sold a big part of his collection for no reason at all.
I sencerely hope it's option 2.(since the lost daggers can be rebought).
Still I do have fate that this dagger could be ok. I must say if you read the story then this looks to be a cunning plan, set to target Mongo. But what if the seller is really thinking (knowing) that it's real.
Would you be as a (private) seller really be intrested to rebuy the dagger , if you could use the cash , or allready has spend it on other pieces? It sounds harsh but I do not think so. (people could call you dishonest , but are you a fraud if the item is real?)
This story may not give you a good feeling, but does not implement it is fake neither.
let's cross fingers and hope Stephen gives Mongo a thumbs up.