It is a threaded flash synchroniser meant to be used with non-synched cameras. It's not supposed to be found on a synched Kiev! 🙂
Got two of these devices, and they are almost impossible to use as they promise. At best they would function as only slightly better than a two-hand open-flash firing at "B"...rather than using two hands, one to fire the shutter and another to fire the flash, the device would allow doing both with one set of fingers from one hand. But they are very difficult to sync with 'instantaneous speeds'. They are supposed to be functional at 1/20 or 1/30, but often the exposures turn out blank- flash fires too soon or too late-
despite doing adjustments or following instructions to the dot.
Jay