This engine used four vernier thruster, Why ?The verniers are for thrust vector control. The main nozzle is fixed in place. Thor used a similar system, but with only two verniers.
The difference was that Thor's main chamber swiveled too, but of course it could only provide pitch/yaw. The twin verniers added roll control, and they also provided three-axis control during a brief vernier-only phase after the main engine shut down.
If the main chamber is fixed, four verniers are typically used to provide three-axis control. There are many examples, most often in Russia, China, India, etc.
- Ed Kyle