can someone help identify and how to test this component
It looks like what you've got there is a capacitor with multiple connections.
It is rated for 600Volts DC, and has the values of 0.4µF, 0.4µF, 2.5µF, and 0.028µF.  

There should be one common lead and four others (five in all.)  From the common to each of the leads you should measure one of the given capacitances.  I can't tell you how to figure out which lead goes with which value.

Don't expect high accuracy - the measured values may be as much as 50% from the given values.  The part itself isn't likely to have been high precision to start with, and will probably have gotten worse as it aged.

You would test the capacitance with a multimeter that has a capacitor function.  The given values should be well within the range of a typical meter.

Checking that it can still withstand 600 Volts is a different problem, and I can't give you an answer for that.

You might check the leakage for the various leads - if it is high then it is bad.  An easy way to check this is to discharge the capacitor (connect all leads together then disconnect them) then measure the DC-resistance from the common to the other leads.  Any low resistance means a shorted capacitor.  This will only tell you if the leakage is catastrophic - it might be high resistance, but still have too much leakage for the circuit to work right.