The Engineering Society crest is typically sewn on the back of the GPA, above the frosh group bar. It is worn by those who have been involved in some way with EngSoc.
Trivia: The crest itself has been around since the early 60's. The lettering above and below the crest where added in 1979 by the then president of the engineering society. Because of the limitations of the electro-set process the time, and the possibility of having had a few pints before starting the work, the curve between the C and I in the upper right hand corner are miss aligned slightly. As an ode to the original mistake, the crest was never amended and continues to be used in its original form to this day, in both digital and physical media.
The mistake can also be seen on the Engineering Society sword in the Tom Harris Student lounge.