[Farmall] Missing Serial Number for Super A?

[Dale]

I have looked very hard for the engine serial number on my new SA, and cannot find it.  I have the tractor number from the seat bracket, but according to the manual, there should be a similar (matching?) one on the right, upper side of the engine block on a flat area below the #1 spark plug.  All I see is a perfectly smooth area about 2" by 3/4".  I scraped all the paint off and see no indication that there ever was a number there.  Am I looking in the wrong place?  Any reason someone might grind off a serial number?  Could the engine be from some other model? Hmmm...  Any guesses?

Thanks,  Dale