Stationery postcard from Madrid to Santander with unlisted censor, 1936

1936 (deceember)  Madrid - Santander.
Stationery postcard Edifil 69 with Santander censor mark "FRENTE POPULAR DE IZQUIERDAS / COMISIÓN DE COMUNICACIONES / CENSURADO / SANTANDER" Heller RS9.1, black. Unlisted censor number "4", similar to Heller RS9.4b (Heller RS9.4b is extremely rare). Stamp lacking and unreadable postmark, but text on the back dated on December 4, 1936.