Unusual Belgian Patriotic/Philatelic Cover

I picked this up at a show a few weeks ago. It's out of my area, but I just found it aesthetically interesting on a number of different levels.

The primary point of interest is the large colorful patriotic (?) cinderella at top right. I've seen examples of this stamp off paper, but never on cover.

At top center there appears to be a revenue stamp, although I'm not absolutely certain that's what it is. If it is, it lends credence to the notion of a philatelic cover.

The back has a receiving stamp from Cote D'Or in France. Also, there is text and a building scene printed on the inside of the envelope. I thought it might be a turned cover, but there's no evidence of postal use or markings.

The text on the inside reads "Grands Magasins de la Samaritaine" above a rendering of a huge multibuilding complex, and then at bottom right below the image:

75 RUE DE RIVOLI
RUES DU PONT NEUF & DE LA MONNAIE
PARIS

Too bad about the staining.

Rather a lot going on here. French shopping compex envelope (I've often wandered past this building) with French WWI cinderella, posted in Belgium years later, with a revenue that presumably has no real place there. Perhaps the original envelope came from the Grands Magasins complete with patriotic stamp. Lovely cover!

And addressed to an employee of the Paris Lyon Mediterranean Railway at a lovely little town in Burgundy. From the employee designation, perhaps the sender knew little about the recipient other than where he worked. Given the traditional rivalry between France and Belgium, posting a cover from Belge with French patriotic material would have been provocative. The use of a cinderella produced in Orleans is also curious.