we get this question almost everyday. the problem is that there are millions upon millions of apps each with their own notification icons. so unless it is a popular app, most of these questions go unanswered.
the easiest way to know what it is is to look into the phone's notifications to see what it is. most of the time though, the op does not have access to the phone. but in your case, it is an old screenshot.
sorry but i have not seen those icons before. the picture is really fuzzy so hard to say. the "s" could be anything. look for apps that start with an "s".