The cards note Thorpe's passing in 1953, so they were definitely made after that.
The French translation mentions finding Spirou stamps on the following products listed and also in Spirou. Spirou is a French comic book with the equivalent of Roobedoes in Dutch. It appears that these comics made stamps in 1988 and in more recent years. These stamps look like postage stamps with comic artwork.
These Thorpe cards were used to promote the umbrella of products listed and also to get kids to buy the Spirou comic books. Point of sale giveaway? Tucked in a newspaper? No clue.
For whatever it's worth, they don't seem that common and point to a series with the numbering, but they sure aren't easy to find.
This is all from a few quick google searches, but my guess would be that these cards are relatively modern, not from the 50s. Again, just a guess based on the mention of stamps. I'm sure you can research the companies listed and pinpoint it more or find more mentions with deep digging. Maybe they are from the 50s, who knows.
Most likely, someone will eventually chime in on here that is an expert on these.