Stokers were those members of a ship’s company who were involved in manning and maintaining the ship’s engines. Originally they quite literally stoked coal into the boilers to power the ship. By World War II coal fired ships were mostly a thing of the past, but the name stuck and even today engine room personnel are known as stokers. As they were in charge of propelling the vessel, stokers were an indispensable part of the ship’s crew and to distinguish this part of the ship’s company, they wore a distinctive branch badge in the form of a three bladed propellor. Once a stoker was qualified, a star was added to this badge and it is an example of this we are looking at today: 

The use of blue printing on white cotton for badges came in during the Second World War and in this case the badge would most likely have been sewn to the sleeve of a pair of overalls. Photographs of men in their overalls are rarer than others as most men changed into their square rig before having formal pictures taken, this photograph, however, shows a pair of stokers on deck in New York. They are both wearing overalls and the white badge with the propellor of their branch can be clearly seen on their sleeves: 

Whilst conditions had certainly improved since coal was removed from service, engine rooms remained greasy, hot and noisy places and the work of a stoker was hard. They were also in one of the most dangerous parts of the ship when in action as they were below the waterline so any critical hits would result in boiling steam filling the engine room, followed by thousands of tons of sea water and little time to get out of the compartment before the ship began to sink.