Check the listing for details. 6-SYLVANIA 6SN7GTB Twin Triode Chrome Top! Black Plate! HICKOK TEST GREAT!. Condition: Used, Made in United States. Listed at 119.99 USD. Offered is a lot of (6) 6SN7GTB Twin Triodes by SYLVANIA. The tubes each test good on the Hickok Mutual Conductance dynamic tester with no shorts or inter-element leakage. These tubes have black angled plates, top halo getters with excellent silver getter flashing on each tube. The tubes have production codes as follows: (2) EK, EL, EM, CB and BJ. Mutual Conductance test readings are as follows: 2650/2850, 2350/2200, 2600/2500, 2500/2550, 2600/2400 and 2400/2750. The good range on the tester goes from 1500 to 3000. Pick up the desirable twin-triode tubes for your own best audio equipment for repair, restoration or upgrade. Mouse over the photo images to zoom in. NO RESERVE!! Thanks for looking.