How to tell Thompson from Thomson

From their first appearance in Tintin in the Congo—serialized May 1930 to June 1931—Thomson and Thompson have been hard to tell apart.

Benoît Peeters got it wrong in Tintin and the World of Hergé. On page 59, Peeters writes “Identical in every way, the two can only be determined by the style of their moustaches: Thomson’s is more rounded and Thompson’s more pointed.”
Herge: The Man Who Created Tintin by Pierre Assouline also gets it backward: “They are absolutely indentical in appearance (black suits, bowler hats, and canes) but can be distinguished by their mustaches. The mustache tips of Thompson (with a p) rise, and those of Thomson (without a p) dip.”

But as our tableau clearly shows, Thompson, with a p, has the rounded mustache and Thomson, without a p, has the pointy mustache. Tintin.com agrees: “Thompson's (X33) is neatly trimmed, whilst Thomson's (X33A) has a distinctive twirl at the ends.” The Tintin Games Book also correctly identifies Thomson and Thompson.

The two detectives were originally called X-33 and X-33 bis in French, which appears in early English translations as X-33 and X-33A.
The early names may be related to the fictional Frau Marie Kolverer, Agent X-27, (played by Marlene Dietrich) in “Dishonored,” a 1931 romantic spy film by Josef von Sternberg. The Kolverer character was inspired by the real spy Mata Hari, codename Agent H-21, and arrested as a German agent in 1917. Or maybe it’s just coincidence.

The two characters were later named Dupont and Dumond in French and Thomson and Thompson in English translations.

Thomson and Thompson appear in only one frame of The Shooting Star, on page 20.
They appear on a 2007 French stamp and a 1943 serialised story “Thomson & Thompson, Detectives,” by Paul Kinnet and illustrated by Hergé.