The seal
Research by the State Archive of Turin (Archivio di Stato di Torino) showed that this seal is an adapted version of the great treaty seal of King Victor Emmanuel II. Impressions of that seal from 1861–1871 are kept in the French diplomatic archives and can be viewed online in the seal database Sigilla. Umberto II only had the name replaced with his own; the rest of the legend is identical.

The seal box
Large wax seals hanging from important documents were protected by a metal case, called a teca or seal box. The seal sat inside, with the cords attaching it to the document running through it. This kept the fragile wax intact while the document travelled to another country.
King Charles Albert of Sardinia (1833–1849) had a special seal box made for treaties, which his son Victor Emmanuel II continued to use. A known example hangs from the ratification of the 1860 treaty by which Savoy and Nice were ceded to France; this document is kept in the archives of the French Ministry of Foreign Affairs at La Courneuve. According to the Turin archive, the box of this seal is a 20th-century reproduction of it. The lid shows a horseman, an image in the long tradition of equestrian seals of the House of Savoy.

A mystery
The seal was never used for treaties. The Turin archive also found no sign that it was used for the noble titles Umberto II granted in exile, and nothing about it was found in his own archive (the Legato Umberto II). Why and when he had it made is therefore unknown. No other examples or matrix are known, so it may be a unique piece – perhaps an experiment that was never continued: a royal treaty seal for a king who could no longer conclude treaties.

Sources:

• Archivio di Stato di Torino, letters of 26-08-2026 (prot. 0005771) and 24-09-2026 (prot. 0006567); dir. Stefano Benedetto, research by dott.ssa Luisa Gentile
• Sigilla, French seal database – seal of Victor Emmanuel II: https://sigilla.irht.cnrs.fr/21942?search=victor%20emmanuel%20II