I recently bought an unused Hodge stripped upper and am curious how to tell if it is the standard or exotic aluminum-lithium alloy version. Mine looks to weigh the same as the exotic, but having paid only $100 via private party I’m 98.5% sure it is not. Still, how can you tell? The pics of the two models look the same. Is there a stamping somewhere to differentiate?

Here is a shot with the HD, a Centurion and a Mega - each weighs 7.6 oz with port door attached.