How to make physically accurate silver in Cycles? I need extremely accurate representation of real world silver in my curren project.

We can approximate "close enought" in cycles, but this time i need it to be accurate.

Other commercial rendering engines have material presets that sampled from real world materials and provide very close approximation. I played around in Redshift, and it have things like IOR, absorption(k), edge tints, that i assume sampled from real world materials.

Cycles just recently go the principled shader, that includes fresnel effect in itself, before that we used handmade tricks to add fresnel to materials. Plus there is no predefined material presets, like other rendering engines have.

Is it possible to make a physically accurate silver shader at all in cycles? I know i can get close enought by adjusting metalness, roughness, adding slight wear etc. But i'm talking about getting real thing, with real values sampled from real world material.
I have one that uses RGB Curves, here are the coords,there are 4 points in the R,G,B and just 2 in color, hope it helps. If not LUXRENDER.

Red = P1(x 0.0, y .96) P2(x .55, y .96) P3(x .83636, y .95) P4(x 1.0, y 1.0)

Green = P1(x 0.0, y .94) P2(x .5, y .94) P3(x .85091, y .94) P4(x 1.0, y 1.0)

Blue = P1(x 0.0, y .91) P2(x .5, y .91) P3(x .81364, y .92) P4(x 1.0, y 1.0)

Color = P1(x 0.0, y 0.0) P2(x 1.0, y 1.0)