Hello,
I've just joined this forum as I need advice in identifying my JLC year and model. It has a screw back, stainless steel case, and looks circa 1950's. I have the case number : 561253, and a watchmaker got a calibre number of : 777933 from the insides. I'm told it's a genuine JLC and has been valued at £1000 replacement for insurance. I'd try JLC direct, but they seem to want an extortionate sum of money just to ID it. The watch is more of sentimental value to me, as it was part of my inheritance.