No copies of original certificates are available—the originals were kept by the seamen to whom they were issued. This information is taken from registers (lists) kept by the customs districts.

The Registers of Seamen's Protection Certificates database contains 30,987 transcribed entries dating from 1796 to 1878. The records document certificates issued through the customs districts of Fall River, Gloucester, Marblehead, New Haven, New London, Newport, and Salem. Entries may identify the seaman's name, age, birthplace, certificate number, date of issue, complexion, height, hair and eye color, citizenship, distinguishing marks, and register image number. The amount of information recorded varies by person and customs district.