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.
You can tell the rough age of the National rice cookers by the design of the logo. If the word “National” is in Helvetica Black, like the Panasonic logo, then it’s late 1960s to early 1970s. Eventually, the name Panasonic supplanted National. If the word “National” is in an older looking, 1930s style typeface, it’s from the early 1960s.
According to Maki Itoh, the first rice cooker was by Toshiba in 1955, and then Matsushita (National) in 1965. The early Toshiba, I believe, is similar to the Tatung Multi Cooker, where you had a heating chamber, and the rice was cooked in a pot within the chamber, and the chamber would be partially filled with water. This would allow the cooker to also be used as a steamer.