Hi Bill
Nice piece.
Do you mean the stuff that holds the blade to the hilt ?
Pitch or tar !
I see they seem to use this as a gum to fix blades also in the East ... Like, for instance, Omani janbiyyas, Indian tulwars and so.
Second thaught
I now don't think you meant that, but the dark "paint" on the blades
.
Please forget my aproach
.
Fdernando