France 1860 20c Chambery Sardinia Piedmont Cover to St. Jean de Maurienne

Folded letter, with partial commercial contents dated 22 August, franked with 20c blue, Type I, tied by Sardinian grid cancel and postmarked Chambery (24 Aug), to St. Jean de Maurienne, no backstamps, piece cut from back to remove wax seal, a scarce usage from what was, until only a few short months prior to the despatch of this cover part of the Kingdom of Sardinia, who ceded the city to France under the Treaty of Turin on 24 March.