Check out this one... auctioned by Czerny's in March 2010, estimated at €18,000, went for €210,000. Then in October of the same year, resold at Sotheby's for more than
€4,200,000!
Czerny's, March 2010
Sotheby's, October 2010
On the hilt, between the ears, the dagger bears what appears to be the Nasrid coat of arms. The same arms (and same maker's mark of an orb-and-cross) appear on other daggers, such as one in the Bargello.