These registers record the service of seamen in the Royal Navy. Records include birthdate, birthplace, vessels served on, and dates of service. The registers include seamen who began their service as early as 1848, with dates of service up through 1928 for most records, though there are a few records with dates post-1939. Make sure to check the image of the original record, where you may also find occupation in service, physical description, reasons for discharge, and other personal details.
You can find details on the system used for assigning service numbers at TNA’s website.