The arrowed screws in the images are the collimation screws that pass to the outside through the housing.
Roof prism binocular collimation.
The system used in binoculars consists of two prisms with at least one prism having a roof edge.
In the most common form of inexpensive binoculars each prism is held in place with a spring clip that tensions it against a screw that tilts the prism.
This can cause eyestrain headaches and a degraded user experience.
Roof prism binocular roof prism binocular is more streamlined as the glasses are in line with one another.
The eccentric ring ajustment is more often found on roof prism bins and is extremely difficult to adjust without the correct equipment and some experience.
Provided the binoculars are not severely out of collimation the collimation is accomplished using the porro prisms housed just in front of the eyepieces.
In a roof prism binocular the prisms reflective surfaces resemble those of a rooftop hence the name.
Contain 2 prisms called dach or dachkanten prism and derive their name from abbe koenig ak prism design.
Normally the collimation is adjusted by screws on porro prism bins which i assume that 20x60s will be.
The prisms are held onto a mounting plate with a metal clip.