u/Beanhands

I just replaced the blade on my XPS01 plunge saw and the depth guide for my XSHO3 circular saw. No problem got the saws back together and started breaking down a 4x8 sheet of plywood. After a few cuts, I noticed this peculiar washer that I don’t remember removing and I cannot for the life of me figure out if it goes to one of the two saws. Looked through the parts digrams and can’t identify it. Anyone familiar with these two saws recognize this thing?