During the 1960’s there were a lot of different LeCoultre Memovox versions for the North American market. Many of them like this World Timer version: manual movement with date and 10K gold filled case.
Actually, the World Timer disk was not that common, but the combination of manual movement and gold filled. Either Calibre 910 without date or Calibre 911 with date. Gold filled – 9K, 10K or 14K gold but most of them without the World Timer indication on the alarm disk.

I suspect no one really knows how many different Memovox versions existed in the North American market during the 1960’s.
This ad from 1969 gives an indication but nothing exact…

Here is an zoom in on the text: …”Like the appointment alarm in each of over 45 LeCoultre Memovox models.”… Over 45 versions!

Not only did the North American market have many different models of the Memovox, they were also sold under many different names – Memovox, Memovox Alarm, Memodate, Beau Brummel, Beau Brummel Alarm, Wrist-alarm…

The World Timer alarm disk were not that common, but more common than on the European Memovox versions. The only vintage European World Timer Memovox was the 3160 released in 1958 as part of the Jaeger-LeCoultre 125 Years Anniversary, a watch we will come back to for sure.
Since then the only Jaeger-LeCoultre World Timer Memovox released was the Master Memovox International in 2010.
Guessing that the World Timer disk were more popular in the North American market due to A) they lived in a country spanning over several time zones, B) more people travelling at that point than in Europe.
The World Timer Memovox were not only used for wrist watches. It was used on travel alarm clocks, pocket watches or like this letter opener.

Here a seen in a wrist watch. Notice the middle watch, reminds of you of another classic watch from another brand? Especially the bezel…

Here, a pocket watch with the time zone cities written in a radiant pattern instead of circular.

Again, these lovely sales pitches, “Today’s businessman often finds himself crossing time zones with the frequency with which he dines.”
Or this one, “Equal to the challenge of space-age mobility…”
This ad is from 1969, during the “space race”, the year of the moon landing!

So how does it work?
“By use of a separate crown this dial can be rotated to coordinate with the hour markers. By lining up the name of the city, in which the wearer is located, with the current time in that zone, a glance at any of the other areas imprinted on the dial will indicate their current corresponding time.”