Turn of the Century fancy. (1800 to 1900 to you youngsters.)
But: It could also be possibly used for a gas floor heater. Fancy free standing one. That is the other possibility.
Seems I remember those as a child. (I love to muddy the water, every once in a while) I think most of the keys had a 1/4 inch square hole in the key for a clock. A little bigger for the gas regulator shaft.
What about a skate key. I remember having some old metal roller skates when I was a kid that used a key about like this to tighten them on the soles of your shoes.
If you compare it to illustrations in Stewart's Standard Guide to Key Collecting, you can find fairly close matches in clock, cabinet, skate, and water keys. I hereby unhesitatingly vote, "Key."
I have no idea whether that's a stylized "W" or mere ornamental scrollwork on the bow of the key. One of your posts mentions Waterbury clock keys, and while some of those do have a sort of "W" silhouette, others don't (or at least it's obscured by another part of the key). Here's an example of each. Not the same sort of key in either case, however. I'll let someone else take up the chase from here.
Thanks everyone for the very informative discussion, It was dug by my parents house, a 1856 home.
Found a CW ammobox breastplate, not far from the key, hope too post some more finds soon, Thanks again