Crossword puzzle clue "where area code 813 is abbr"

Where area code 813 is: Abbr.

Area code 801 area

Number that begins with an area code: Abbr.

Secret code, in the secret code

Code hidden in a bar code

Its area code is 907

Assiniboia area code, to Calpernia

New Jersey area code, in ancient Rome (oh, did you want to do Roman numeral math? That's what I thought)