(1) Tested Zenith 6KT8 Tube High Mu Triode Sharp Cutoff Pentode Tube

(1) Tested RCA 6CB6 Tube RCA Sharp Cut Off Pentode Tube (b)

(1) Tested RCA 6CB6 Tube Sharp Cut Off Pentode RCA 6CB6 Tube (d)

(1) Tested RCA 6CX8 Tube with Box Date Code CR Medium Mu Triode Pentode Tube

(1) Tested RCA 6DT6 Tube Sharp Cut Off Pentode Tube

(1) Tested RCA 6AU8 Tube with Box Date Code KQ Triode Pentode Tube

(1) Tested RCA 6AU6 Tube Code GR Sharp Cut Off Pentode Vintage Tube

(1) Tested RCA 6CB6 Tube Sharp Cut Off Pentode RCA 6CB6 Tube (c)