Which Floyd nut fits my ESP neck?

[brunning]

I have an 1986 ESP neck that i picked up for a project (reverse hockey stick headstock, nice meaty frets, wide neck).

When i got it, it had a Floyd R2 (1-5/8" wide) nut that obviously did not fit right, the nut was too narrow. I figured it obviously needed an R4 (1-11/16"), so i pulled one out of the parts bin, but found that was too narrow, as well.

Turns out the nut slot is 1-6/8" wide. what locknut is this?

[gpenguins]

See if this helps - I didn't really check out the sizes, I just know the page existed:

http://www.floydrose.com/nutsizes.html