There's a serial number printed (or written) inside the Kiev camera near the shutter release latch. I've worked on 7 cameras and I have noticed no relation with the one printed on the top plate. See picture, the s/n is 10250 whereas we can read 518796 on the top plate. Nethertheless, in some cases they match. There's some samples in DVDtechnik collection. Very weird.
Shutter or shutter assembly serial # possibly? I know Moment shutters for example have their own serial #, I don't see why Kievs wouldn't.... just a guess...
I have heard that the number inside is actually a date when that part was installed. So, Oct, 2, 1950. Probably the camera wasn't completed until early 1951, when it was given a serial number. However, that does not explain the cameras that have a matching inside number and serial number.
My 1950 Zeiss parts Kiev II 500097 has a number 178 on the shutter frame. I have other two with 27199 and 947, but I forgot the camera model. They seem to be parts number.