Three comments
1) Both items are of fine quality and highly desirable. We could not afford both and had to decide. Should we bid on the other one it would have realized very high price as well.
2) Why this one: As already mentioned, primarily the high quality wootz. It is Persian wootz with dark pattern and high contrast. Not very common on Ottoman daggers. The curved blade on this type of daggers is not so common as the straight one and also the very high quality silver work on the scabbard was a factor. We are almost sure that the other dagger also have a wootz blade but may be of a lesser quality.
3) Hippo tusk: Has already mentioned both handles here are walrus ivory with the very characteristic marble like inner core. Walrus tusk was the favorable material for handles in the Ottoman arsenal (as well as the Persian one). Hippo tusk handles are found sometimes on Indian and Indonesian blades. It is characterized by a line of tinny dots, looks as if the tusk is made of two halves of slightly different tint glued together. With age the dots are getting dark and looks like a line of black points. See for example a handle of an 18 C. Indian Jambiya dagger:
and another one, a handle of a Javanese Badek dagger:
