Good day OF, i recently acquired a gold Longines manual wind dress watch, and was unable to open the case to determine if it's a 14/18k gold or fully gold plated.. Longines has identified it to be a cal 280 plated gold watch made in 1966. It would be greatly appreciated if I could get some confirmation on this as I have never come across a fully gold plated one with a gold caseback, most of them are on a stainless steel one. The only picture of the caseback is attached, rather blurry unfortunately. I don't see the 18k inscription on it. Thank you and an advance Happy New Year to all ☺
In the case back is engraved, “Plaque Or 40 Microns”. This means, Gold Plated, 40 microns thick. I do not know the fineness of the gold used, but it is little consequence. Hope this helps, gatorcpa