Yes, what you are seeing is the Roman numeral character for the number one (1) in the serial number. In the example I posted there are two places where that Roman numeral is used. But, if you look at my second attachment it shows the Vehicle Number assignments by model year and location .... NONE of them have a Roman Numeral in them ..... but you can decode the Vehicle Number on a P15, P17, P18, P19 or P20 by using that chart to determine place of origin.
Good luck ....