The Stronglight alloy cotterless cranks were introduced in 1933. The logos on the most popular model, 49d, changed slightly over the years some more drastic than others. Very subtle variations can be seen in the “S” and “G”. In the 1950s the logo deleted the word “Marque” from the logo, and then inexplicitly brought the “Marque” back in the logo soon after the introduction of the Super Competition Mod. 63 cranks in 1963.
In the photograph, the oldest crank arm is at the bottom, from the 1930s, and the one at the top is from the 1970s. Along with the logo stamping subtleties, the profiling and milling of the crank arms also changed over the years.