FN numbers are no longer issued, [ last FN number issued was in June 2007 ] - used to be issued to NICOP holders in SINDH with foreign remittance certificate issued by embassy of Pakistan in the country of residency. They get exemption from paying the Income tax [ now called withholding tax ] at time of registration during those days
CN numbers in SINDH are issued to Private registered Pickup trucks, Vans, & Box cars. [ Yellow plate Black alpha numerics ]
I was at excise office for a vehicle registration this afternoon and got an update in this respect
& the wording BOXFILE at website means the Original file has been returned to owner.