Coat of Arms of Coucy - messengers badge?

[fernando]

Originally Posted by fernando

Perhaps a bit too large for a vervelle.

Going back into the period, a vervelle could either be an (heraldic) adornment to attach to a belt or to a horse harness. The ones i have spotted so far are slightly smaller than Adreas example.
I guess many reasons could originate its falling off. If in fact it was an implement adorning any part of a knight's personal ot horse's gear, it could have been ripped out while in combat.
On the other hand, we can't exclude the possibility that, wherever it was riveted, belt, harness, box, armor, uniform, someone took it off ... and temporarily keep it as a trophy.