This is a flashgun attachment, 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 in its original box.
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).
This accessory is described in the very useful Land List
website.