Mr nibbs your blackberry is gps enabled, It puts the coords to the exact location the photo is taken, as metadata on your photos. I would advise turning it off to protect yourself and your sites.
It doesn't look like Wrought iron to me, that would help with dating it, can you tell? Wrought iron usually has a stringy appearance like you see on old anchor rings. I've seen a similar piece on an old wood burning stove, but those were almost always cast iron. The piece of the stove also had a hinged door on it. Can you see any evidence of hinges being mounted on the flat bottom of the arch? The size and shape are very close, but that is my only guess.
Good luck,
Jason
PS - LostCauses is correct, I pulled the GPS coordinates of where those pics were taken out of the meta data header of the image. Be careful!
It may be the front plate to the fire box hole that the stokers would shovel coal into, but I think it is pretty small for that and only 3 rivets chances are I am wrong. ( I was wrong once before, LOL).
ZDD
The first thing that came to my mind when I looked at the picture is the face of a parking meter. I'll have to see if I can find a pic to show you what I mean.