Did You Know That there is a series of postcards of La Belgique Historique
I came across it quite by accident: postcards with a small explanation in French of the publisher DESAIX. They carry a nice stamp (but there are also without). More I have not (yet) found out.
Unfortunately these cards are hard to find and my collection is far from complete. However, now that I have more than 10, it was the right time to show them in my collection:
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