Farmall Cub

The serial number plate on my tractor is in rough shape and I am trying to determine exactly which is the serial number. In the center of the serial plate is the engraved number 1666 followed by a large "J". Along the bottom of the serial number plate is the engraved number 1575.
Which of these is the serial number and what does the other number mean. Also, how can I confirm that this is a 100 as opposed to a 130 or something using either serial numbers or components?
And I did check the Serial numbers on this site and both of these numbers falls into the 1954 model year if it is indeed a Farmall 100, which I would like to confirm
Thanks
Ramon

Check casting date codes. There will be on most of the larger castings. They should mostly have Z for the year. They look like (*6.21.Z*). This example would be June 21, 1954.

Jim,
I just checked and the information is as follows:
The codes underneath the spark plugs was
"C123"
Firing Order..."
"11 30 Z"
The code to the right of the battery was
"357657R"
"L 2 6 Z

It sure sounds like a 1954 and the engine size seems to be stamped on there... although if the numbers preceding the Z are dates, its a little confusing...

November 30 and February 6. Often they are closer than that, but I wouldn't consider these dates to be that unusual.