6su7gty 6188 tung-sol tube preamp tubes black round plate pair  test strong

two tubes = 2 pieces = two valves type 6su7gty 6188 tung-sol 

 tested on tube tester TV7D/U 

test results as follow 

tube 1 = 40 & 48  code 3227-52 

tube 2 = 44 & 44  code 322403-3

(reference good at 30 & 30) 

 brown base & round plate on both tubes 

box 174