No but really, why is she looking at him with a complicated look? Picking apart stuff in class is perfectly normal, however would you otherwise learn anything (about how pens are constructed)?!
Though if it is because he squandered a spring by playing with it, I kinda get it. Each time you see someone do that, you can easily predict in your mind "he's gonna lose it". Hell, it even applies to if you play with a spring yourself: "I'm gonna end up losing this, aren't I?". Doesn't make it so you have the option to not play with it though, so her reaction is still odd.