About this detail of the Tiger
The weapons of a tank need to be calibrated with their optics. In Panzers this was a delicate operation, for trained personnel only. They would use a distant aiming point (over 1km away) or else they would aim at specially drawn targets on a sheet or panel ("die Richttafel"). There were separate sheets for the turret and for the hull MG.
This is the turret calibration sheet for a Tiger 1. The left-hand cross targets are for the telescopes of the TZF9b binocular gunsight. In 1944, after the monocular TZF9c arrived, the outer target was not used. The other targets are for the main gun and the MG respectively. This image links to a larger diagram that copies the full specification, translated to English.
When a manual was drawn up for the Tiger's turret in mid 1943, the calibration sheet was specified in it [1, see plate 62] as a 1/5 scale dimensioned copy.
To calibrate the weapons, the crew would carefully park the tank, using a spirit level to ensure that the main gun was level in the side-to-side direction. They would place the relevant sheet 50m ahead of the vehicle on the line of fire. The thick vertical line on the sheet was aligned with a plumb line to make the sheet horizontal.
The guns and sights were then lined up on their targets. The crewman or armourer would peer through the gun barrels to align them. In the case of the main gun, two crossed wires were temporarily fixed to its muzzle to mark its precise center.
This is the sheet for the hull MG, which is also defined in the Turret Manual [1, see plate 63] . Here, the hull machine-gun was aligned to the upper target, and its telescopic sight to the lower one. This is curious because the telescope was mounted at exactly the same height in the tank as the MG, but its target is lower down on the sheet. That is to allow for the fall of shot over a distance of 200 meters [1, see page 48] .
Because the hull MG and telescope needed different elevations, it was not possible to calibrate them by pointing at a distant object. Use of this sheet was mandatory. Fall-of-shot was an issue for the turret weapons too, but the gunner would correct for it with his TZF telescope.