VTG Brass Letter "O" From Old Building Sign, Advertising Sand Cast?

I have hijacked my husband's Ebay account to put up some items that must be cleared out! I have been selling for years under the name Margeauxchanning, but I've been helping a friend sell her vintage items. So, for accounting reasons, I'm keeping our items separate. Check them out!
I have had this mixed bag of brass (bronze?) letters for at least 10 years, and FINALLY I dragged them out to sell. If any of you are from Italy and want to buy them all, they spell GENOA.
This auction is for the letter, O. Yes, you're buying a VOWEL! These look so wonderful on a shelf mixed in with books and other treasures.
From the dimples back of the letter, and the texture at the corners of this letter, I'm thinking it's sand-cast. DO let me know if I'm wrong!
It measures just over 6 inches tall, and 6 inches across, but check the photos I took with the letter next to a ruler, and you'll get a precise idea of the sizes. You can see in the next to the last photo that this E is more than a 1/2 inch thick.
It was on a building somewhere-- don't know what kind.
I bought these letters from a high end antique dealer who had a garage full of things she was liquidating. I kept thinking I would use them to decorate but I never did.
Many thanks for looking and I LOVE to combine items to save you shipping costs!