This is the steam nozzle cover, a part that attaches to the center of the underside of the lid of an Asahi Kasei pressure cooker "Katsuryoku Nabe (SW type)". The included accessory is the O-ring fitted inside. This is a used part taken from a 2008 model SW 5.5L pot. There are no noticeable scratches or stains. This is a common part for the SW type and can be used with both the deep 5.5L pot and the shallow 3.0L pot. It has a different shape from the current mainstream ZK type and cannot be installed. #mmkz41's list of Katsuryoku Nabe parts for sale