Which kind of component uses an "EM" symbol prefix, has a value, and three pins?
It's probably a 3 pin EMI filter like this but pin 2 isn't used: -

There's just a hint of circular clearance around the middle pin where the copper plane is removed (within the silk screen rectangular outline for EM3): -

It's possible that it's a C-L-C type where the centre-pin is a common point for the two outer pin capacitors and also there's an inductor between the two outer pins as well hence C-L-C.
If you could show a side view picture it might become clearer.