Spanish Civil War Encased Postage Token?

Sap the Forgetful needs your help once again. I'm certain I posted this question here on CCF back when I acquired this piece almost exactly a year ago, because the pictures were still sitting there in my "previously downloaded images" file, but blowed if I can find the old thread now. I don't even know which sub-forum I'd have posted it in, but it rightly belongs here in Tokens and Exonumia.

It's an encased postage stamp from Spain, sometime in or shortly after the Civil War period.

The stamp is a red "El Cid" 10 centimos, issued by the Nationalist faction sometime around 1939. The case is aluminium, and the stamp is protected and held in place by what appears to be a strip of clear photographic film, complete with sprocket-holes.

The back of the casing has the words "Mallorcalzados, Mallorca 259, Junto Paseo Gracia". I initially thought that the use of "Mallorca" meant it must have come from the island of that name, also known as Majorca in the Balearic Islands. But I seem to recall someone here on the forum pointing out that the "Mallorcalzados" is either a shop, a street or a mall in Barcelona, on the Spanish mainland? Barcelona is the only place in Spain listed in my World Notgeld book recorded as having issued "encased or unencased stamp money".

It may not even be a real encased postage token; for all I know, it's just somebody who recycled an old milk bottle top to help keep their stamps nice and dry. But I bought it in a coin dealer's scratchtray, so we'll assume it's numismatic until I'm told otherwise.

Any ideas?