Oh, it's quite obvious. It's a look that Benjamin hasn't seen, except perhaps for the very first time they met, running into each other in that park - but that had been no where near this extreme.

And yet, it's something for Benjamin to latch onto, to shake him out of his own shock and grab on to this other man as though he were a lifeline.

Well. It isn't as though he hasn't already done that already, to some degree, but in this case, it's specific. That look is shock, but it's also knowledge. Harding has realized something, and Benjamin suspects that is the same thing that he's trying to grasp.

"This is familiar, the metal, the mechanical... You know it too, you must, it's - as it should be."

As soon as Benjamin says it, he knows that it's true. It's the feeling that he's been trying to figure out since that first echo that'd told him that his other self wasn't human, since he'd seen Chris's own robotic arms, since receiving X-ray vision.

"It's the rest of me that isn't."