The range marks on the T-55 sights do not seem functional.
First screenshot is taken by the gunner turned out ranging a target tank with binocular range finders, 1030M
Second Screenshot is using the range estimate brackets while in zoom 1 view, range estimates show greater than 4Km (target is far left tank, under 40 bracket)
Third Screenshot is in zoom 2, brackets estimate 1.5Km (far left tank, under 14 bracket)
Also of note, commanders cupola ranging sights do not change with zoom either which makes them non functional I believe?