I might have solved the mystery of the prefix letter on the engine serial numbers in the kittens,
first, the serial prefix and number does not matchup to the automotive numbers,
next the prefix, S does not show up in English Ford automotive numbering, and Experts confirm this info
the S prefix most likely refers to "Stationary", as engines used in saw mills, water pumps, aux generator sets, etc
very very little info has been found other than finding serval such setups and their serials also had the same prefix "S"
so little basturds serial is S61019 E and that is a most likely a 1952, maybe '51, serial number, making it the earliest known kitten serial number