Rare Stamps & Postal History of the World

1860 20c gray blue, horizontal strip of three, unused without gum, reasonable margins to just touching in places, very fresh and virtually v.f., signed Raybaudi, Diena, etc., with 2019 Dr.Avi certificate ("unused multiples of this stamp are extremely rare") (Sass.20c) (catalogued as three singles without gum $11,400, Sass. €21,000, without any consideration for the multiple rarity)
Estimate: $1000