Unfortunately I bought three pairs of these brakes a couple of years ago thinking that they were the finer more refined "LS" (I think that was the name) model.
The calipers currently on offer on Ebay look dreadfully like my "investments". I do not think that Weinmann would wish to acknowledge having made them, as the finish is not up to that company's standards.
Those calipers that I bought were thicker in the arms than the Swiss maker's and more poorly finished. If I had to hasard a guess I would place them as a Taiwanese product from a company such as Chang-Star.
As for the date of their I think it would be in the very late 70s or early 80s...probably one of the last throws of the dice before Mafac closed down.
Norris Lockley...Settle UK