Your cameo is lovely! Heart shaped cameos are not all that common. Congratulations!
Your cameo is of Italian origin and was made after 1968. The features and hairstyle of the lady in profile attests to the modern style.
NA is the province abbreviation for Naples - Italy and it could have been made in the city of Torre Del Greco, in Naples, famous for it's cameo carving. The three digit number will be the registered number of the gold smith.
The engraving on the reverse of the cameo material would be the name or signature of the carver.
