I wonder if     anyone is familiar with the construction of the above
device? In german it is called "Baurahmen" and enables the beekeeper to
see activity on the comb without opening the hive. According to H.Storch
in his book "At the Hive Entrance" it is widely used in Germany, but
unfortunately the only description he provides is, " the glass pane of
the window is arranged facing towards the inside of the hive (in Winter)
and the free space filled with corrugated paper for insulation. ...In
the summer, the building frame is positioned with a starter strip of
foundation, and then the window galss outside>"
 
I cannot envisage how this is constructed as to simply replace the side
of an existing super with glass will be of no use to observe activity in
the winter time.
 
Peter Wright