Confirm Camera B is a Kiev-4 like the one I have. Yours was manufactured in 1976 and considered an average good production while mine was made in early 1980, quite not the same.
In 1981 the quality was so bad that high-brasses came from Moscow and sent the whole production to the city garbage location.
Camera C is a Kiev-4a, made in 1972. I had one of those too but never worked.