numbers on gold-filled eyeglasses

[flyfisherman]

Hi guys!I got a some old gold-filled eye glasses frames ,they are from Spain and instead of normal 1/10 or 1/20 GF marks those marked 20/1000.Does it mean 20 microns,and if so what is the difference between microns and microinches?

 

[qst42know]

I haven't seen that fraction used but I have seen 1/50, 20/1000 is the same thing.

 

[flyfisherman]

I doubt that 20/1000 =1/50.The gold foils on these frames does not look five times thiner than 1/10 GF.I still think 20/1000 is equal to 20 microns .

 

[qst42know]

Gold filled is a karat gold content per unit of weight. Gold filled is not expressed as thickness. Mathmatically 20/1000 = 1/50.

Are these marked G.F. or not?

 

[flyfisherman]

I dont remember if those were marked GF or not ,i cut them into pieces for processing some time ago.Glasses frames could be gold-filled and not marked GF.I found few italian one that simply said 18 k,and they there GF.Besides if we belive to wikipedia 20/1000 mark on eyeglasses is representing profound low vision(world health organization eye vision scale).It is hard to say for sure what those marks really mean :?: