on the movement indicates that is was produced when JLC & VC were being imported and then assembled (movement into case) in the US by Longines-Wittnauer. There are posts from the 2003-2004 years on this forum that go into great detail about this relationship, which was set up to avoid US Customs.
This is most likely a late 60's/early 70's piece.
The movement look like a Lemania 321, but could be a Valjoux (I don't know the specifics to point out, but I'm sure any of the watchmakers on this forum could nail it in a heartbeat).
I like the fact that the bezel is a "count-down" bezel and not an "elapsed-time" as is the case most often.
-Dean
Open your case back, and see what's written Inside. Very often, the ref number is written INSIDE the case back, on Lecoultre watches.
Best,
Nicolas.