The round barrel Uberti carbines have that sight (all of their octagon barrel guns have a dovetailed front sight). On '73's the sight is sort of angular with a sloping top and straight down in the rear. The versions they put on '66's is round, like a semicircle.
Nope, not adjustable, and the rear ladder sights are not elevation adjustable, either (not counting the ladder, but that is only for further distances than CAS).
I've added a brass bead to all three of my '73 carbines.
And yes, some of the original carbines had the integral sight/barrel band, while others had the sight attached to the barrel behind the barrel band.