I am looking for the serial # for the engine on my Super 55. I see 3 sets of numbers on the left side of the engine block behind the carb. The numbers are 180220E, F12354, and IL 100B. Are any of these the engine serial number? I was also researching the tractor specification number. My spec # is 15-0005. I have found that 15-0001 and 15-0002 are for gas tractors with different size tires and -003 and -004 are for diesel tractors with different size tires. I can't find any info on a 15-0005 spec number. Can anyone help? Thanks.