Wow had you posted this in the Longines sub-forum and did I miss it. I don’t know anything about Longines in the 50s but from @Tony C.’s very good article I seem to recall Longines chronometers were rare in those years.
Don’t quote me on it though, better check for yourself.
Best S
TGIF! 🤪
145.012 on my new Rally strap from Lugs.Shop! It arrived in Toronto Canada from France in 7 days without a hitch! Great online experience! Thanks Guillaume 👍