Today we have Zenit TTL which was introduced in 1976. Made in USSR.
TTL means Through The Lens. This camera was Zenit's first device with this type of light measurement. Light meter was now in a prism, making it possible to read the value, looking through the viewfinder.
Setting the exposure you had to average the clock needle between + and - to besure that the lightening is well done.
P.S. Zofia helped me a lot with lighting of this photo.