engine ID help

I recieved this post from the Innocenti list and have looked through my
limited data resources.  Anyone able to help Julio?

Geoff Branch
'74 Meejit "Yellow Peril"
'72 Innocenti 1300 Mini

PLEASE HELP ME . I OWN A 1975 INNOCENTI MINI COPPER EXPORT 1300,
THE ENGINE NUMBER IS 12HC21AA  101446. I KNOW THAT THE '12 MEANS 1275CC AND
THE "H" IS HIGH COMPRESSION BUT WHAT DOES THE "C" STAND FOR ?

                                           THANKS JULIO