Serebrianka is a Russian hop, which is reputed as the father of Cascade. Cascade was released in 1972, in the early stages of detente between the Soviet Union and the USA. Whether the splicing relates to this is anyone's guess.
Serebrianka as a name indicates the growing region (like Hallertauer), in Kursk Oblast in Southern Russia. Incidentally the name translates into Russian as 'silvery', or 'smooth-tongue'.
I actually have some of these in my freezer, bought in Russia.