Wash. Rev. Code § 19.84.020
Any person who shall sell or issue to any person engaged in any trade, business or profession, any stamp, trading stamp, cash discount stamp, check, ticket, coupon, or other similar device which will entitle the holder thereof, on presentation thereof either singly or in definite number, to receive either directly from the vendor or indirectly through any other person, money or goods, wares or merchandise, shall, upon presentation, redeem the same either in goods, wares or merchandise, or in cash, good and lawful money of the United States, at the option of the holder thereof, and any number of such stamps, trading stamps, cash discount stamps, checks, tickets, coupons, or other similar devices shall be redeemed as hereinbefore set forth, at the value in cents printed upon the face thereof, and it shall not be necessary for the holder thereof to have any stipulated number of the same before demand for redemption may be made, but they shall be redeemed in any number, when presented, at the value in cents printed upon the face thereof, as hereinbefore provided.
RCW 19.84.020