I have searched for answers to this question as well myself, the best that i could come up with was that "fn" indicates that a jewelry item is plated with a "finish"...... Basically fn is an opaque way of saying the item isn't real gold, just plated.
Code FN shown on display and function on equipment not working .
The FN key stands for function and then your f1 f2 ...... keys Also, in mathematics it stands for Fibonacci number, Fn. But you probably mean on the computer keyboard.
Foot Note
There is no Fn on the periodic table of elements. However, there is Fm, Fermium, number 100.
What does this mean in jewelry?
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a part of the sn
Fn = Fn-1 + Fn-2
what does cor means in jewelry
Andel Jewelry Corp
Nickle plated