The National Thoroughbred Racing Association (NTRA) announced Wednesday that vouchers worth $2.69 million--including a $1-million grand prize--have been mailed to more than 540,000 racing fans as part of this week's NTRA Mystery Mutuel Voucher promotion.The voucher giveaway is the NTRA's ninth such promotion dating back to August 2000. The vouchers are redeemable for cash on Aug. 14 at participating racetracks and OTBs.The vouchers are coded tickets worth from $2 to $1 million that are distributed via direct mail, accompanied by customized brochures. The average voucher is worth $4.96. During the first eight Mystery Mutuel Voucher promotions, more than $25 million worth of vouchers have been circulated, resulting in double-digit increases in pari-mutuel handle and attendance at most participating sites compared to the same weekend date from the prior year.The voucher redemption this weekend coincides with major stakes, including the Arlington Million (gr. IT) at Arlington Park and the Sword Dancer Invitational Handicap (gr. IT) at Saratoga."Given past redemption rates that far exceed the marketing industry norm, we think the Mystery Mutuel Voucher promotion remains one of the most effective direct mail initiatives in all of sports," said Keith Chamblin, NTRA senior vice president-industry relations and marketing.The 18 sites participating are: Arlington Park, Bay Meadows, Canterbury Park, Churchill Downs, Del Mar, Delaware Park, Hawthorne Race Course, Hoosier Park, Los Alamitos, Louisiana Downs, Monmouth Park, Mountaineer Park, Oaklawn Park, Prairie Meadows, Sam Houston Race Park, Sports Haven (New Haven, Conn.), Suffolk Downs, and Woodbine.