I read it as 48? Anyway it refers to the year of the Emporor's reign, so 48 = year 48 Showa = 1973. This is your coin: http://en.numista.com/catalogue/pieces1589.html
Oh, BTW for future reference the site has calender converters for non gregorian dates, also Creativity Time Machine has date converters for even the most obscure calenders.