Soviet 8-pin ceramic socket PL8-2K with snap ring is rsh5-1 type that fits the following tubes:
12SK7, 1540, 1851, 5881/6L6WGC, 5881WXT, 5AR4, 5U4GBEH, 5Y3GT, 5Y3GT, 5Y3GT/G, 5C3S, 6550C SED, 6550EH, 6550WE, 6AB7, 6AC7, 6AG7, 6AG7, 6AS7G, 6B4G, 6B4GEH, 6B8, 6BQ6 GT, 6CA7 EH, 6H6, 6H8M, 6J5, 6J7, 6K6 GT, 6L6GC, 6L6GC, 6L7, 6Q7, 6SH7, 6SH7, 6SJ7, 6SJ7, 6SK7 GT/G, 6SL7, 6SN7EH, 6ST7, 6V6, 6V6GT, 6V6GT EH, 6W4 GT, 6A7, 6E5S, 6N13S, 6N7S, 6N8S, 6N9S, 6P3S, 6P3S-E, 6P6S, 6S2S, 6S4S, EL34, EL34, EL509, KT66, KT88, PL36, SG3S, SG4S etc.

Silver-plated contacts!