Reference 3150 was the very first alarm wristwatch offered by Jaeger LeCoultre.
Produced only from 1949 to 1952 with these distinctive , gorgeous tubular lugs. My own research shows evidence of sales starting in 1950 and officially being announced in 1951 Basel Watch Fair. The serial number 648802 on the movement of my Memovox puts this exactly in the first 6 Months of 1949, making it one of the first Memovoxes ever produced!
The patent document pending by JLC for the Memovox in 1949 also featured the case to be elevated on the wrist, hence case back never directly sitting on the wrist with the tubular lugs raising it , thus achieving higher resonance for the alarm than had it sat flat.