Leica DMIL 160 objectives, and it's focusing

[microb]

The older Leica DMIL with the Leitz tri/binoculars takes 160 objectives. The turret moves up and down like an infinity inverted, which for infinity makes sense because changing that length to the telan lens does not matter. But with 160 objectives, how does that work? Wouldn't moving the objective and changing the distance ruin the focus?

To extend the path across the bottom, there are two doublets. Most likely they collimate and then restore it to 160 for the trinocular.

[microb]

Here's a diagram someone sent me, so I augmented it.

[apochronaut]

Do those two doublets travel at all, or are they fixed?

[microb]

They are fixed, and lens two has the flat side, possibly slightly concave, facing the camera. I got the drawing wrong.

The doublets are different sizes, not identical. The second is slightly smaller.