Leitz Wetzlar VIOOH Imarect finder for 35mm to 135mm focal lengths and adjusts parallax from 3.5ft to infinity.
It is the so called "straight-sided" VIOOH finder of the postwar production, including 8.5cm index.
To use with Leica screw mount and M-series rangefinder cameras with an accessory.
The affixable Leitz Universal Viewfinder serves to determine the field of view when using interchangeable Leica lenses f=3,5 cm to 13,5 cm. It shows the respective frame in a sharply defined field after switching to the used focal. The main index mark on the knurled setting ring clicks in at the available focals. The viewfinder then shows the border for all object distances over 1,50m.

At a shorter object distance the smaller index mark next to the larger one (see the enlarged drawing) can be set, which compensates for the smaller field of view that comes into play with close-distance pictures.

(Parallax compensation see reverse.)

The parallax (the result of the misalignment between the optical axes of the lens and viewfinder) that comes into play at close focus can be compensated by the parallax calculator (2). With shots at over 4m the dial can be set at the distance scale's infinity mark (∞), because the parallax takes effect only at object distances under 4m, the correct setting of which needs to be observed, so that the viewfinder image corresponds with the object field.

Scheme of the parallax compensation

Ocular
Parallax setting
Placement foot
Foot for flash or light meter
Setting ring with range
Prefix lens for 2,8 cm focal
LEITZ Universal Viewfinder VIOOH
Corresponding leather case EBOOH
Prefix lens for 2,8 cm focal TUVOO