Spec'd and imported by Masi USA, built in Italy, possibly painted domesticly, one of two second tier frames, other being the Gran Corsa, don't know the pecking order for sure. The images would not fully load for me, so I did not see the serial number, might have the system of: quarter of the year, by alpha (a being the first quarter) followed by the last two digits of the year, then a number of for the X frame for that quarter.
I suspect mid later 80's, these bikes fight for respect but appear quite nice. At this point they are probably undervalued.