This is a Marukan Minimal Thermo. It's for temperature control and is used by connecting it to a heater. Operation has been confirmed. I bought it for about 4000 yen. The warranty period has expired. There is no box or instruction manual. I stopped using it after about a year because I switched to a smart home. The cover on the tip of the thermo was chewed by a lovebird. I would like to sell it to someone who is okay with that. The actual device is shown in photos 6 and later. Photos 11-12 show the bite marks. It has been stored at home. *It is also listed on other sites, so it may be deleted or canceled without notice.