6EU7 RCA gray ribbed plates NOS 1970 era

51/32 

52/32

(6EU7=12AX7 with non-tapped filament of 6.3V wired to pins #1 and #2 to reduce hum; claimed to be quieter than 12AX7)

Recommended for

- Echoplex

- Sherwood

- Gibson GA-5