A detail makes all the difference, between the very first Memovox, the Ref 3150, and all the other which came later: The shape of the lugs.
As you will see on the pictures posted here, the lugs are tubular.
And if you pay attention to the pictures, you wil notice that the case back is not " sitting ", but elevated on the wearer's wrist, in order to enhance the resonnance of the Alarm.
The 3150 was produced from 1950 to 1952, and, according to Zaf Basha, was officially introduced to the Public at the Basel Fair Watch in 1951.
This reference houses a Cal 489, which is manual winding movement, 17 jewels, beating at 18 000 vibrations per hour, with a power reserve of 45 hours and an autonomy of 20 seconds for the Alarm.
This reference came with different dial variations:
Nr 1, painted numbers:
Nr 2, Applied numbers and indexes:
Nr 3, applied indexes only:
It also came in solid gold, as pictured below:
I don't have the numbers of production for this reference, though.
What is important to say is that the JLC Memovox ref 3150 was not the first Alarm wrist watch released, as the anteriority has to be credited to Eterna, and to Vulcain ( 1947 for Vulcain ), which received ( the Vulcain ) the nickname of the Presidents Watch, because some US Presidents wore it.
But no other brand than JLC offered such a diversity of Alarm watches, and the with the 3150, the Legend is starting!