ECC91 = 6J6

Equivalent 6J6, 6J6L, 6101, 6CC31, HF202S, M8081, TS52
Near equivalent  
With different Vf XCC91 = 5J6
CV number CV858, CV2843, CV4031, CV8160, CV8231
Swedish Mil.nr. M2462-427
M2462-504, M2462-509C
Tektronix part no 154-0032-00