Qrt.S,
I am sending another photo of the Kokoshnik. It looks a little strange under magnification. Possibly a scratch or writing between the head and Assayers letters.
I also have a silver salt dish with E. Prokofev marks.
The city hallmark is #2019 in Postnikova.
It is probably a fake, since it does not have any assay mark. Maybe E. P. Prokofev was a popular silversmith to copy.