Cal 453 with sub-seconds and its sister cal 454 with center seconds were based on the JLC 449 ebauche. After their merger in 1938, all wristwatch movements were sourced from JLC other than chronographs. The 18th jewel is a lower cap jewel for the escape wheel pivot, an upgrade shared with cal 1007.
I think their story rises above fashion. These watches were conceived in ecstasy for the 150th anniversary, yet born into the economic depression of 1935. A way to turn over unused lepine pocket watch movements at a good price. Charles Constantin credited this model with returning the factory to ful