Steamship Designations / Prefixes (Merchant Vessels)

Ships during the late 1800s through 1950s all had a prefix. The most common prefixes appear below.

• S.S. for Steamship (Steam Ship) This is the default designation
• R.M.S. for Royal Mail Ship / Royal Mail Steamer
• M.S. for Motor Ship or Mail Steamer
• M.V. for Motor Vessel
• R.M.M.V. for Royal Mail Motor Vessel
• T.S.S. for Twin-Screw / Triple Screw Propulsion Ship

You will often see documents from the same voyage using different designations such as S.S. "Steamship" and R.M.S. "Steamship."