[1] Ratings in the Royal Navy include trade badges on the right sleeve to indicate a specific job.
One star indicates they have passed the required exam in order to be eligible to be selected for the Leading Rates course in their respective branch.
Two stars indicates they have completed the Leading Rates course and are now eligible to study for the Petty Officers (PO) Professional Qualifying Exam (PQE).
[2] Ratings in the Marine Engineering and Medical branches may obtain "Dolphins" (qualify for the Royal Navy Submarine Service).
Some personnel have an additional option to pass the All Arms Commando Course and serve attached to the Royal Marines.
In 1920, petty officers with four years' standing also received the fore-and-aft rig with the cap badge formerly worn by CPOs.
Chevrons on the left sleeve, below the rank badge, are for long service and good conduct (one for each four-year period; no more than three may be worn).