I initially picked this up from a hacker space assuming it's a toroid, and could not find any specs for it.
It has 4 terminals, which I assumed would be connected to each other in pairs.
Measuring resistances didn't help, they all showed some resistance about 1.5k ohms.

What can this component be?
The number of the component reads NA-25 0125

I googled it, but I'm not sure what I'm looking for.

 

Hi,
I think it is a Hall effect sensor.
http://www.newark.com/fw-bell/na25/hall-effect-current-sensor/dp/28C7972

 

Thank you for the help.