| Number item | Description | Number item | Description |
| a | Serial number of that engine in the year of manufacture | b | Engine type |
| c | Number of cylinders (where required) | d | Code letter Z or A - Anticlock rotation |
| e | Year of manufacture (add to 1950) | f | Code letter R - Radiator cooled |
| g | Code letter S - Seawater cooled (not used much) | h | Code letter M - Marine auxiliary |
| j | Code letter MG - Marine propulsion | k | Code letter MP - Marine propulsion |
| m | Code letter MGR - Marine propulsion with reduction gear | n | Code letter V - Engines for Lister-built gensets |
| p | Build number - always prefixed by a dash ( - ) | | Letter 'S' IMMEDIATELY after engine type letters = Turbo |
