This is a 1970s or 80s Solait yogurt maker. It is an insulated housing within which you put a quart jar with your warm milk and yogurt starter. Cover it up and leave overnight and in the morning you have yogurt. No electricity needed. Works great and you can leave the yogurt in there for longer amounts of time than overnight. There is a thin crack on the outside but it does not affect the functionality at all. This is a great item if you are living off the grid and want to conserve electricity. Does not include glass jar but these are readily available.
eBay