Things are ALWAYS worth what someone else is willing to pay for them. Go out and try to sell your Yen coin and see what you can get.
Your 1993 coin is worth $1.08. Most big banks will convert it to dollars for you, but at a slight charge.<br />
A currency converter which plugs in current exchange rates:<br />
Ask Google:<br />
100 Yen = 1,0792 US$
thirty cents, about.
Take it into a reputable coin dealer -- they should give you an estimate for free. Probably not much, seeing it's not all that old, but you never know.