According to the parts catalogues, Royal Enfield started using this speedometer in the autumn of 1941. It replaced the S114B speedometer, with “slide on” speedometer- cable fixing and with “Eng. Jaeger Patent ” text on the dial face.
On the other hand, according to the velobanjogent, "the shield logo" in the picture above was used up until the mid 1946, when the circular "MA" was removed and the text became SmithS with the "S" at either end in capitals. From the mid 1950's, but more likely 1959 on, the logo was SMITHS...
This was the "universal" speedometer that replaced all the different meters that had been used so far. This "standardisation" was also applied to the saddles, the horns, the batteries, ...
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