bike-race betting ticket
Specifically a ticket for betting on keirin (競輪) bicycle races. Not used for other types of race betting.
I bought a bike-race betting ticket at the keirin track.
車検 (vehicle inspection) and 車券 (a betting ticket for keirin bicycle racing) are pronounced identically but refer to completely unrelated things.
Compound of 車 (sha, 'vehicle, bicycle') and 券 (ken, 'ticket'). The reading しゃけん follows standard on'yomi.