With the periscope mounting sandblasted and all clean it was assembled to see how it all works.
This portion is exposed on the armoured car. With the periscope removed the circular inner tube can be rotated and closed off.
The serrations and spring loaded plunger that locks the inner tube in various positions, it is rotated via the thumb latch seen on the right.
Looking into the housing one can see the periscope retention catch, in this position the periscope can be inserted into the housing.
And here you can see the catch rotated, in this position the periscope would be locked in place.
A left hand side view, the thumb latch seen on this end is for locking the periscope in place.
The right hand side showing the details.