Does anyone know what this is? It looks like a handstamped surcharge, but not the same kind as the 1946 Provisionals. I say this because the letters seem to read MO, which is probably the beginning of the word MONS. So I'm wondering if it was a special local surcharge.
The stamp seems to have been cancelled in 42 but it could just as well be 47.
I can't read the name of the cancelling office: ------ SUR-MARGILENNE perhaps?

Thanks for looking!