This item is a Minox FL4 Flash Cube holder. It mounts to various Minox cameras (Minox A, B, C, BL, LX). The unit comes in the original box with the instructions and leatherette case.

I am including 3 packages of three unused flash cubes (total 36 flash bulbs) with this flash cube holder. 

It originally used a Mercury-based PX-27 battery, which is no longer available. I have generally replaced this with a stack of 4 LR43 button batteries in other cameras that have called out this battery. I have not tested this flash unit. However, it appears like new, never used and all battery contacts are clean, without any sign of corrosion.

When this flash unit is used on a Minox A or B, the shutter should be set to 1/20. On a Minox C or BL, it should be set to 1/30. On a Minox LX, it should be set to the flash position on the shutter dial.

Please note that I show the unit mounted on a Minox LX camera but the camera is not included in the sale, just the flash unit and flash cubes.