Part of the original chateau?!

Every now and then we come across a piece of old stone that has been carved. Eduardo who is now digging out the earth floor in the west wing of the chateau found just such a stone. No idea what it is or where it could have been. The room that it was found under dates from the early to mid 1500's so it certainly predates this. We have previously found carved window surrounds and small decorations or swirls carved into the stone.