Re: Brought to you by the letter "A"
Since this "A" is marked STERLING, it might clean-up using Wright's Silver Polish. If not, your local jewelry store should be able to clean it safely. After it is clean, check the back for any nibs where a pin or loop could have been. In your pic, it looks like a nib at the top. Also check to see if there are any tiny holes in it. I have seen mounted sterling letters on jewelry boxes, silver flatware boxes, etc. I feel like it's probably a pin, brooch, or pendant. Is there a symbol in front or back of the word sterling? Breezie