Back then, their was a thing in the UK called "The pool". This was simply the Local Shipping Office. You were either a 'Pool' man or a Company man.
If a man needed work, he would go down to The pool and see what was on offer. If he saw a vacancy which suited him, he would go to the desk and apply for it.
The master of the ship had to sign an agreement with every single member of the crew.(inked rubber signature stamps were a Godsend). The Articles of Agreement were signed by each crew member in front of the local Superintendent of the Shipping Office. Normally these articles were for a single voyage or for 2 years. Each deck crew member had to have appropriate proof of past experience. This would have been submitted before signing-on. Other than two certificated engineers, the engine room staff did not have to have any statutory qualifications.
In ships crewed by colonials, in India or Hong Cong for example, the procedure was a bit different but essentially the same.
The Official Log book contained a list of Crew Members. Against each name, the master made a conduct report. A Decline to Report was a nasty . On the other hand, a seaman could opt to have the lesser notation.. ENR... Endorsement Not Required. All was not lost though. The seaman could appeal against the master's report and the Superintendent mentioned earlier would look into the circumstances. If he thought fit, he could issue the seaman with a certificate indicating that in his opinion, the DR was unjustified.