Stencil looks like Carabinieri. Rich A. in Pa.
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Knowledge is power, guard it well.
It looks like an M-33 in Carabinieri colors. Usually a monogram inside circle on decal....may have been removed.
The Carabinieri, although police, are technically a corps of the Italian army....Arma dei Carabinieri.
Maybe our Italian experts can confirm or add to this.
Have a look at this site: ITALIANO 33 COM
It would help if you could post pictures of the interior, it could just as easily be post-war.