See scans
The stamp is signed Cotta and one other, but I do not know the second signature
The condition of the gum of Italian stamps from this period is difficult to judge.
In my experience, Italian experts tend to consider a stamp like this mint never hinged.
I have priced it as mint lightly hinged, although there is no obvious trace of a hinge.
Stamp has the "SAGGIO" overprint, which means "Proof".
This is Sassone # 13
Sassone CV for a stamp without overprint is 2000.00 Euros for hinged and 3000.00 Euros for MNH.
The "Proofs" should be at least as rare as the regular stamps with the cheaper ones trading at a premium.