Provided you have OFP version 1.91, you can use a trigger like this to get the class name of any object (using it's object ID):
Trigger
Radius: 0,0
Condition: Radio Alpha
Condition Field: this
OnActivation Field: hint format ["%1",typeOf (object XXXX)]
Where XXXX is the ID number of the object you want the class name of.
With this just bear in mind that some objects (ie. bushes) don't have class names. When you try that method, no hint will pop up.