It's usually printed on a sticker that's in the service log book. Trouble is people tear them out and "put them somewhere safe" (lose them). Next owner is then stuffed first time the battery's disconnected and the radio requires the number input. Hope this helps. good luck.
Chris.
July 2007
Hello Keith
Take the radio out of the dash board and you'll fin the serial number on a sticker on the metal casing. It will probably begin with M followed by a six digit number.
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