Not a bolt, a nut sorry..
I found this specialty nut in the driveway where I park my Disco2... Does anyone recognize it?? Thanks
I think it goes with something that uses a cotter pin.. maybe tie-rod end or something..

 

I don't know where it goes but have some observations about the nut. It doesn't go with a cotter pin because none of the notches line up across from each other. I believe it's called a castle nut. The top notched area is crimped in so that it will be tight going on. Something like a lock nut. Wish I could be more help but that's all I know. D*

 

I thought same thing.. looked like notches for a cotter pin but they don't line up..

 

What size (diameter) thread in millimetres? or what size across the flats. It looks initially like the staked nut off the front or rear hub centres. There are no castellated nuts on a D2 only staked nuts. Unfortunately the coin is blurred and so hard to estimate the nut size. If it is a hub nut it needs replacing PDQ.

 

Without the coin for comparison, i would say check your tie rod ends. Is that a quarter?.

 

Suggestion. Post another photo or two with a 6" rule alongside the nut with the rule graduations clearly visible. Obviously it isn't a castellated nut or a nyloc nut my guess being a stake nut which has been used multiple times and damaged.

https://www.google.fr/search?q=disco...hrome&ie=UTF-8