Registers of Certificates of Service of masters and mates aboard foreign-going British merchant ships kept by the General Registry and Record Office of Seamen (RGSS) and its successor. These volumes register certificates which were awarded to already serving officers. They compliment other British archives registers of Merchant seaman. The cards on Ancestry.com are the application records held by the National Maritime Museum. Our records in most cases include later or correct records on a seaman's service. Our research guide explains more on the Merchant Seaman records we hold: https://www.nationalarchives.gov.uk/help-with-your-research/research-guides/officers-merchant-navy/ We will add further records as we go along. There are approximately 130 films to be transcribed.