The funny thing is that at the time that the "Calculus Affair" was being published in Tintin magazine from 1954 to 1956, there were no covers showing scenes from the story.
When the magazine published the previous adventure, "Destination Moon" and "Explorers", there were several covers illustrating the fact. An early cover showed the technician about to strike Calculus' helmet, but seen from another angle than that shown in the story itself (see
ebay). There was also another showing Haddock struggling in his space suit.
The Tintin magazine covers from the "Calculus Affair" period would primarily feature scenes from other stories by various artists, such as Graton, Macherot, or Reding. Covers drawn by Herge would only show Tintin, Haddock, Snowy, Calculus and the Thompsons for special occasions such as Easter and Christmas. They also appeared when the issue was about cars.
For example, the cover for the 42nd issue of 1955 has Tintin and the others unveiling a Fiat 1100 which was to be the first prize in a competition. Inside the issue, we have the scenes from page 42 of "Affair", from Wagg interrupting Haddock's conversation with Nestor to Snowy snatching a man's umbrella.
You would have thought that, given the fact that Tintin was the titular star of the magazine, they would have had some covers advertising the adventure, a scene of the spy running out of Calculus' laboratory (book page 15), for example. When "Tintin in Tibet" started publication in issue 38 of 1958, the cover had Haddock and Tintin finding the Yeti footprints in the snow.
Strange that the magazine's editors did not have covers publicising "Calculus Affair". I suppose that it was fairer for the other contributors but it's curious all the same.