The Register of Seamen survives for this period so it may be worthwhile visiting The National Archives. The register consists of two large card indexes (BT 348 and BT 349) which are available on microfilm. They give place and date of birth, ships served on, and, sometimes next of kin.

In 1941, when the next register was being prepared, cards were extracted from BT 348 and BT 349 for seamen who intended to serve during World War Two. These extracted cards can be found in series BT 364 and BT 372

At some time in the past, a partial attempt was made to bring BT 348, BT 349 and BT 350 together, resulting in a further class of records known as BT 364. Cards are organised in Discharge 'A' number sequence. If you know a ship on which a seaman sailed, and can find the agreement and crew list, this may provide you with the Discharge 'A' number.

Merchant seamen: Registers of service 1913-1972

Merchant seamen: Medals and honours

For a fee of £3.50 you can access records of World War Two Medals (BT 395 ) claimed and issued to more than 100,000 Merchant Seamen from 1946 to 2002 in DocumentsOnline.

My Ancestor was a Merchant Seaman, Second Edition, Christopher T. Watts and Michael J. Watts (Society of Genealogists)