The stamping on the back is the manufacturer of the case. I'm not sure off the top of my head who that is. I'll post if I run accross it.
Most USA market cases were made by U.S. case contractors, in particular when the cases were made of 14k or gold filled.
Thanks again, Zafbasha! I am really digging the history unraveling on this watch. Below is a post reply I had received over on Reddit which was quite informative. Seems to be on the ball information wise. It’s a fairly long read but was helpful, your catalog find just links up perfectly to this reply.
“Beautiful, and in flawless condition. That's a really great classic watch.
As to production period, I can narrow it down on age a bit, and point out some cues for dating JLCs of this period.
First, one key aspect is the antishock device. On this watch, that's the clover shaped gold colored spring seen on top or the cap jewel on the balance assemoly. Fine balance has the highest rotational speed of any component in the watch, and needs a fair amount of mass since it's the consistency of this oscillation which makes for precision.
So, to avoid slowing down the motion and expending a lot of energy, the speed means the balance staff pivots need to be quite fine. But, since these pivots must also support something with reasonable mass, the fine pivots can be easily damaged or broken by a mechanical shock, such as from bumping or dropping the watch. This has always been a risk on watches, and it was made worse by the transition to wrist watches since they're now in a position to get banged into things much more easily than pocket watches were.
In early watches, one of the most common causes of failure was broken balance pivots. There were a few attempts to address this, with mixed success, in the 1930s, including things like flexible arms on the balance wheel, allowing the rim to displace without applying as much force on the staff, but it wasn't until the 1940s that really effective methods went mainstream.
These techniques involved spring loading the cap jewel on the balance wheel so that when the balance staff is displaced by a mechanical shock, the jewel moves and flexes on its mounting, instead of being rigidly supported allowing the balance staff pivot to collide hard enough to be bent or even shattered.
The first style of these used by JLC, the early Parechoc KIF A, had a leaf spring type mechanism mounted on a rotatable stud the balance cock, which could be pivoted into place during assembly, applying a spring load and retaining the cap jewel via a ring-shaped section of the spring.
The second type, also made by Parechoc (an antishock device manufacturer located in la Sentier, where JLC is located) also called the KIF, and later "Flector" antishock system was introduced in 1956, and that's precisely what’s in that movement. So, from just the balance assembly, it can't be older than 1956.
On this movement, the escape wheel cap jewel is also equipped with an antishock device, and this one is of an even later design, a lyre spring type introduced by Parechoc in 1957 called the "Duo-Fix". So, that moves the earliest date this could have been made up another year.
And, finally, there's the K819 designation of the movement itself, which was introduced in 1959. So, I would say this watch is from the very late 1950s through the 1960s, and most likely, based on style, early 1960s.
Forentine finishes on watches were popular in the very late 1950s and early 1960s, too, so the style fits well with that assessment.
The latest date would be the 1970s, when JLC retired the "LeCoultre" trademark which had continued to be used on US market watches since the 1930s following the merger of Jaeger and LeCoultre, and began branding all watches as "Jaeger-LeCoultre". The last US market LeCoultre branded watch was made in 1976. But, your watch absolutely drips early 1960s style, from the Florentined case and bracelet to the finishing on the movement, so I don't think it was made any later than that.”
