Looks like some kind of license plate.

I picked this sign up at an estate sale in Dallas a couple of weeks ago. It doesn't look like any license plates I've seen online. The letters are bolted on, not embossed and there is a small tag that reads "Ace" on the top-left hand corner of the sign. I'd love to know about how old this sign is and what it might have belonged to and how much it may be worth. Any help would be greatly appreciated. Thanks!