Or... did you mean you found one of those washers and your not sure where it goes other than this spot?
I don't see an image or anything in your post, so wasn't sure.
Pretty sure it's 2 of the belleville washers and they face each other to act as a spring. One turn too much and they go flat/become useless. Had a very narrow window of "right" vs "wrong" with those.
This is from the old 2.5R revo manual I have on my PC: