As you suspect, this looks to me like a WWII period "tax duty paid" seal for a pack of cigarettes.
Judging by the "Rampant Lion" insignia in the centre and the language on the seal, my guess is that this is of Belgian origin.
Hello, Czech and Belgian lion are very similar. This is but 100% the Belgian lion and war time Belgian cigarette stamp.
1.00 Fr. = 1 (belgian) franc. In Czechoslovakia, the currency was always only crown (koruna = K - Kc - Kcs).
Inscriptions on right side are "Prix and Prijs" ("price" in French and (your) Flemish language).
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