This is a flashgun, model 490, a focused flash system that used Hi-Power flashcubes only, which were put inside the device. It was designed for use with 400-series folding pack cameras.
It is called a focused flash system due to the set of louvers in front of the flashgun, which are coupled to the focusing mechanism in order to alter the flash's light output (depending on the distance to the subject).
It is in its original box, with two Eveready AAA batteries (which have now been removed from the instrument).
This accessory is described in the very useful Land List
website.