Our early Kiev cameras same or simular? Maybe the first three models.
The Kievs are very similar to the ContaxII, some ContaxII have Kievs parts, as there are no Contax II spares.
The Contax IIa ribbons are rather different, the Kiev ribbon is not exactly the same as the Contax II ribbon but can be bodged to fit a Contax II.
This may be variation in Kiev ribbon!
Early Kievs are expensive.
There is some variation in Kiev cassettes but all mine fit in Contax II and IIa.
A Nikon wide should fit and work ok on most Kievs, Kiev wides normally (25%) need rebuilding to fit on Kievs! The J12 won't fit on any IIa.
Interchangeability (parts) is not warranted Kiev to Kiev, Swiss files are useful.
Same is true of Contax I...
If you get an early Kiev it is just as good for photos as a II or IIa most meters still work ok even 70s are nice shooters.
There are two important variations in the Contax I. The earliest model has no slow shutter speeds, and its rangefinder assembly uses mirrors and prisms.
The later Contax I had slow shutter speeds and uses only prisms in the rangefinder system.
Both cameras have two eyepieces - one for focusing and one for composing your photo. However, the focusing-composing eyepieces are reversed in the two cameras. In one camera, the focusing eyepiece is on the left, and on the other camera it is on the right.
The later camera also feels more refined and more solid. The early camera, feels -- to me -- a bit rough in operation.