ALL FORD VEHICLES, including the 9N, 2N, and early 8N tractors, used the STAR (*) symbol in engine block serial number prefix and suffix designations. The star symbol denoted that steel cylinder liners (sleeves) were used. In early 1950, FORD then switched to cast iron sleeves and engine block serial numbers now used the <> Diamond symbol in the prefix and suffix of the s/n. An early N would have had the .040 sleeves, BUT, that is a moot point nowadays. You won't know what you have until you break down the engine and see for yourself, meaning DO NOT GO OUT AND BUY ANY NEW PARTS just yet if this the intent of your question. They do not make nor sell steel cylinder liners anymore so cast iron is the only option no matter what now. Get the block stripped and verify what you have first -chances are it has been rebuilt at least once in its life, maybe not, but don't guess.
FORD ENGINE BLOCK SERIAL NUMBER HAND STAMPS: