These are car ashtrays sold in the after market in the 20s and 30s. They originally had suction cups screwed in that hole and often times had metal lids with holes. They are quite collectable and often found advertised in the insulator section. Some of them have a nickel plated bracket that attached to a round object in the car. These were produced by Akro Agate, Houze, and other companies. They come in a variety of forms and some are quite pricey. (thanks to Jim Sinsley for this info)