I have looked and looked for a serial number on my newly aquired tractor. The block says 8 N (cant read anything else). On one side of the trumpet I can read 9N 4013-B, under it reads B and then a hexagon. When I look at the serial number identification it says I should have more numbers but I have throughly cleaned it and can't find any more numbers. Am I overlooking something? Any help would be greatly appreciated.