Produced in the late 50’s in the USA, large reflector folding to a minimum size, mainly orientated to Minox A at the time. The Minox B followed shortly in production and it was used on those cameras as well. However, there was this issue with the flash lip touching the meter on the B model, so an ingenious device was made to avoid this, namely “the lock plate”, or “shield”.
The lock plate was basically a small aluminium plate, was put over the end of the B camera, where the meter button is, so the flash lip did not touch the button. A thin slot in the plate ensured the flash catch onto it, holding in the position. As the plate had a hole in it, where the meter button sat, the button never got pushed accidentally.
In the photograph below, you can see the catch of the flash unit, which engages the slot onto the plate. The catch engaged and disengaged the plate by turning the dial seen here, in open or lock positions.
The flash unit used AG1 bulbs, and was powered by a mercury battery, AA size, now extinct.