Please Help ID accessory?

[MicroBalrog]

What is this thing on top of the AKS-74U?

 

[SDC]

It looks like a 2nd-generation night-scope; my best guess at least.

 

[MicroBalrog]

What's a second-generation night scope?

 

[Preacherman]

The son or daughter of a couple of first-generation night scopes?

 

[SDC]

Oops, sorry. A 2nd-gen night scope is an image-intensifying telescopic sight, that lets you aim and fire in the dark, in light conditions where you wouldn't normally be able to see your target with the naked eye. The 1st generation (if I have my history right) were the "Vampir"-type infrared sets used in WW2 and Korea, where the rifleman needed a projector to beam infrared light out towards a target, and a scope capable of picking up that light that was reflected back; the M3 Carbine is the classic example. The 2nd generation didn't need to use an infrared projector anymore, because they take the existing light that's bouncing around out there, and run it through an intensifier to "multiply" it, so you can see what/who's out there without advertising your presence (using a 1st gen setup when the other side also has night vision stuff is like waving a searchlight around and banging a drum). The newest (3rd gen) stuff is basically a solid-state, miniaturized version of the 2nd gen equipment, so you don't have a huge piece of gear to lug around (as per your picture). HTH.