Posted: 17/01/2014 at 23:00
If it has some antique value it is generally better not to clean anything off until you know what you've got, in case you remove too much important material. I know it's too late for that now but I think it still could be worth an professional opinion.
I'm wondering if it could be what I think was called a 'fire-dog' - a removable little metal shelf from Victorian and Edwardian times, that clipped on to the front of the grate of an open fire to rest a kettle or similar vessel on (a) to boil up the water or (b) to keep it hot after it had boiled. It looks a bit 'art nouveau'.
My grandmother had a couple of these which she used in the winter when the fire was lit. I seem to remember they were quite ornate pieces of cast iron. If it is a fire-dog there should be evidence of there having once been another metal casting coming off at right angles from the wide end ( at the bottom of your picture). This would have been the bit that clipped onto the grate and the piece you have would have been the bit the kettle rested on. That's if it is a fire-dog!