This is the second time I've seen this.....

I "think" both times it was while removing the magpul single point sling from a Colt LE trade-in rifle.

I say think as I found the other piece sitting on my bench so I can't be sure. However this time, I was replacing the magpul single point sling endplate on my latest rifle and this piece fell out while blowing through the staking.

Never seen this piece before, does anyone know its purpose and if it is part of the magpul sling setup?

This is the best picture I could get. It doesn't appear sheared on either end, but I am certain it fell out from somewhere when I was replacing the end plate.