Dating late 19th and early 20th century coins requires more skill than can be given here.
Most pre-20th century coins are undated and depend on the ruling emperor of the time.
Coins from some provinces used the Arabic AH system of dating (see Dating Arabic coins section for help).
Other coins had the ‘regnal’ system, depending on the ruler/government/occupier/regime of the time. Help on identifying and converting numbers can be gained from the Dating Japanese coins section. The numbers are the same and are read from right to left.