Era Trio

Hi everyone,

Here are some nice rarities I found localy in Ukraine.
Era-12, Era-14 and Era-15

https://img-fotki.yandex.ru/get/5407/18405597.22/0_108313_f09fd7af_L

https://img-fotki.yandex.ru/get/6406/18405597.22/0_108314_199a57f3_L

https://img-fotki.yandex.ru/get/4205/18405597.22/0_108315_67c404c3_L

https://img-fotki.yandex.ru/get/6802/18405597.22/0_108316_b87e0bf2_L

https://img-fotki.yandex.ru/get/3913/18405597.22/0_108317_9b673e7e_L

https://img-fotki.yandex.ru/get/6604/18405597.22/0_108318_6868e978_L

https://img-fotki.yandex.ru/get/17914/18405597.22/0_108319_e18a89b3_L

https://img-fotki.yandex.ru/get/9828/18405597.22/0_10831a_5825002e_L

https://img-fotki.yandex.ru/get/5105/18405597.22/0_10831b_84db6e18_L

They are still at my friend's home, he did the photos, but I wonder if one of you had more infos about it.

I only found infos in Volosov's big book "Fotografi4eskaya Optika"
It was designed by E. Grigorieva, I. Driatskaya and S. Frolova (3 women).
It was kind of high end reproduction lenses with very high resolution power.
Lens design is 6 elements in 4 groups.

Pity, it's not written when they have been designed. Bt in the book, Volosov say that "during the last years[...] was asked to develop high resolution lenses" (sorry, very fast traduction). His book was released in 1978, so I believe that my exemplars are close to first years.
Anyone one have more info about it?
Date of conception, for what machine / camera it was designed?

Thanks!