Good photoshop selenium curves?

Does anyone have a nice set of photoshop duotne, tritone or quadtone curves to emulate the look of a selenium toned print? Or know of a third party plugin that does this?

I've been starting with the preset photoshop tritone of black, cool grey 10 and warm grey 1, but just can't capture the same look of a real selenium print.

Any suggestions would be appreciated!