Quote Originally Posted by Mediocre View Post
The way it protrudes out, it may be for grounding purposes. Rubber ring would make sense then also
it's possible as then it would contact the back cover in three places the two on the ring and the one by the battery cover could make a circuit maybe ..

have know of casio that need the back on to work can't think which models but sure have had that in the past .. if I had the back cover it might shiny a light on to that but came in a tat lot I only keep it as it was a 1980's SO-11 so not that common model . the front has damage to the glass on the edges in several places but that seem to be the norm from what I saw .