This was not part of a rice cooker. It is a rice pot. To use it, it was put over heat. The rim and lid were designed so that starchy, boiling water would not overflow down the sides.
It’s such an unusual piece. My best guess is that it was brought over from Japan in the 1940s or 1950s. There were other vintage rice cookers for sale at this thrift shop, so I’m guessing someone passed away and had their hoard donated. The rice cookers I bought were a National Rice O Mat from the early 1960s, and parts for a larger, chrome Rice-O-Mat of the same vintage.
To buy, search Ebay: Aluminum Rice Pot