Dear David Green,
Thank you for posting your question to History Hub!
A great place for you to start your research would be with the Immigration and Naturalization Records held in the National Archives. A guide to those records can be found here: https://www.archives.gov/research/immigration.
As far as the issuing agency of the certificate, you may be in luck! The National Archives at St. Louis houses the Merchant Marines Personnel and Licensing Records; 1967 and Prior, which are part of Record Group 26 (Records of the United States Coast Guard). Here's an article with more information: https://www.archives.gov/news/articles/merchant-marine-records-document-maritime-service
This series consists of individual files containing papers documenting the service of merchant seamen licensed by the United States in 1967 or prior. Each file consists of an envelope/jacket which provides the following information: name and address of seaman, place and date of birth, and license numbers. It also contains, the name of vessels served and seaman status is noted. Also included is certification of identification number (“Z” number), continuous discharge book number, date and place issued, dates of renewal, and date and place of issue of other certifications. The record consists of applications, certifications, licenses, and correspondence. The record may contain photographs, birth certificates, and documents related to union membership.
For more information on this series, you can email email@example.com.
Under normal circumstances, the process for requesting these records is fairly simple. However, due to the COVID-19 Pandemic, and our limited workforce, we are prioritizing requests from veterans and their families for medical emergencies, final military honors, and other essential benefits. Currently, there is a substantial backlog of routine requests, in addition to the emergency requests awaiting response. While it is still unknown how soon we will able to resume responding to routine requests, the National Archives at St. Louis is working hard and taking an aggressive approach to decreasing response times and eliminating the backlog. Please understand, that your request will be placed into a queue for non-emergency requests until such time as we are able to process it.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RRPO (The National Archives at St. Louis). We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck with your research!