Coins offered to the kami. They are usually thrown into the offertory box (saisen-bako) which may be located at the shrine or, in a portable version, taken on the shinko-shiki. At the toka (tenth day of the new year) ebisu of the Nishininomiya Ebisu shrine near Osaka, worshippers press coins into a large fresh tuna provided for the purpose.
See Saimotsu.
A Popular Dictionary of Shinto. Brian Bocking.