Can you help to identify these frames, bikes or parts?

I've had a look at the frame, which is an Eddy Merckx. It all looks legit, very light etc, and all the pantographs are there along with a visible frame number. My only concern is that the brake bridge at the back doesn't have anything panto'd on it and is not the same shape as other Merckx's that I've seen.

Were all Merckx frames made with the fancy bridge or were some made with normal ones?

Does anyone have any tips or tricks for identifying SLX tubing from SL or lower grade tubing? I'm going to check out a frame later and I don't want to trust the decal badge alone. I've read on another forum SLX tubes have rifling (the twisted effect you get in a gun barrel) in them so I should look in the fork steerer tube for it. Is that true? Anyone have some SLX forks they could check on for me? Or any other ways to spot genuine SLX?

Thanks