Sentence:  The St. Louis club is the only nine in the league which gives its patrons the right to see a full game or no pay. In Chicago and other cities, after the first inning is interrupted by rain the spectators are supposed to have received their money's worth. In St. Louis ‘<WSD>rain checks</WSD>' are issued in such cases. 
Meaning of the word marked with <WSD> tags:  Any voucher or note from a merchant to a customer to provide an item the merchant has run out of at a later date for the item's current price, or (in a more literal sense) to provide a service at a later date.