op(box(x)) --> box, but is(op(box(x)) = box) --> false.

• Subject: op(box(x)) --> box, but is(op(box(x)) = box) --> false.
• From: David R Stoutemyer
• Date: Sat, 05 Nov 2011 14:10:12 -1000

op(box(x)) --> box, but is(op(box(x)) = box) --> false.
 
Also is(op(box(x)) = 'box) --> false,
and is(op(box(x)) = "box") --> false.
 
How can I programmatically detect that op(expression) is box? 

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