(1) Tested RCA 6S4A Tube and Box Date Code KP Medium Mu Triode Tube

(1) Tested Dumont 6S4A Tube Date Code 61-26 Medium Mu Triode Tube

(1) Tested Very Strong RCA 6GN8 Tube with Box Date Code DL High Mu Triode Tube

(1) Tested RCA 6AZ8 Tube with Box Date Code KG Medium Mu Triode Cutoff Pentode

(1) Tested RCA 6J6 Tube with Box RCA Medium Mu Twin Triode Tube (b)

(1) Tested RCA 6CW4 Tube Nuvistor Tube with Box Date Code 039 High Mu Triode

(1) Tested GE 6S4A Tube Date Code 63-43 General Electric Medium Mu Triode Tube

(1) Tested RCA 5BR8 Tube with Box Date Code AQ Medium Mu Triode Cutoff Pentode