Louis the eagle that you have is in the M1842 pattern for the Garde Grenadier. However it lacks the detail and depth of an actual helmet eagle Wappen. As Brian mentioned above these helmet Wappen were stamped out on two piece die on a press under extreme pressure. There was no cutting out required, just cleaning up of the sheared off edges. In fact if you pick up any helmet Wappen and look at the edges with magnification, you can see how it was sheared off from the die.
So Louis I have no idea what your Garde Grenadier eagle plate is. Consider a different use, like a grave marker, a book cover, a plaque of some sort. Who knows? It still is a very nice piece.
The one on eBay however is almost certainly an attempt at a fake, as die press stamps require great skill and are very expensive, so this was ‘probably’ someone’s attempt at making one that failed.
