Dear Ms. Hann,
Thank you for posting your request on History Hub!
The Merchant Marine Personnel and Licensing Records dated prior to 1968 in the Records of the U.S. Coast Guard (Record Group 26) are in the custody of the National Archives at St. Louis (RL-SL). Please contact RL-SL via email at firstname.lastname@example.org. Include the name, date of birth, dates of service, “Z” number, and date of death, if known, in your request.
We hope this is helpful. Best of luck with your family research!