If the VIN started with the letter "M", that means it was manufactured somewhere in South-East Asia. So odds are that is not the VIN but a chassis or coach serial number. Look around and see if you can find the coach manufactures data plate. That usually has all the info like model, serial number and maybe even the VIN. If no luck, check in all the cabinets and glove boxes for any coach manufacture's part, build or outfitting sheet, as they may have the VIN listed.
There usually is a VIN Plate, so it may just take systematically checking everywhere.