UBB.threads Forums Edged Weapons Miscellaneous Dagger Forum NPEA Potsdam Dagger Value

I have a NPEA dagger that with the assigned number of P410, I have found it to be from the Potsdam School. I am looking to sell it. I took it to a gun show in Dallas, TX. I heard a seller speaking German and it caught my attention. I asked him if he knew anything about my dagger. As soon as I handed it to him, he replied that it was a fake! He handed it back to me then asked to see it again. He took the handle apart and saw proof marks that changed his mind. I was walking around this busy gun show with it in my back pocket! He told me to take better care in protecting it. I thanked him for his proofing and history lesson. As I walked away, he offered to buy it. He stated $1k, I thanked him and stated I was just wanting info and walked on. He found me several rows away and upped his bid to $1,500! I passed and continued with the show. He stated he had a buyer at $2,000.
What is a true value of this dagger? Where would one go to sell it at a fair value?