from my documentation papers:
OFFICIAL NUMBER: for all vessels, the official number shown on the COD (Certificate of Documentation) preceded by the abbreviation "NO" must be marked in block type Arabic numerals at least 3" high on some clearly visible interior structural part of the hull. The number must be permenatly affixed so that alteration,removal, or replacement would be obvious and cause some scarring or damage the surrounding hull area.
NAME AND HAILING PORT: For RECREATION vessels, the name and hailing port both must be marker together on some clearly visible exterior part of the hull. All must be at least 4" in height made in clearly legible letters. Hailing port MUST include BOTH a place (city) AND the state.
I guess I better make sure my numbers are in there next spring..glad I was never boarded last year....