What is this on an M48A2? Looking to do a good detaling.

Yeah, I like Tamaya, but this was a gift, so... hooray Monogram.  Thanks for the extra information, though!

But more to the point, that "ledge" below it is lousy excuse for what is actually a pipe grab rail that stands clear of the turret surface.

Move on to the Tamiya, Revell or Dragon Pattons. There's no comparison.

Ah, cool!  Very interesting.  Thanks for the info.

That's part of the rangefinder, an armored housing, I  believe. There should be a slot on each one for the lens. 

Hello!

While I'm sure Rob can tell you much more about it, the armored bulge houses the optics of the stereoscopic rangefinder. It basically compares pictures from two scopes (hence two bulges) and using the angle between almost parallel scopes that show the pictures being very close to one another it calculates the distance from the target, which you need to accurately aim the main gun.

https://en.wikipedia.org/wiki/Coincidence_rangefinder

Those bulges should have a narrow, vertical slot in their fronts, that's where the scopes sit. Good luck with your build and have a nice day

Paweł