"Showa" refers to Emperor Hirohito after his death in 1987. Japanese custom dictates that an Emperor's name is changed after death. So your token might date post-1987 as Showa (Enlightened Peace) would likely not have been in use before then. Yes, perhaps a token like those elongated pennies to be stamped at some amusement park or event. The question is, are there similar tokens but of different U.S. states?