Can anybody help me identify the quality of these tubes?
Hey guys! First post here so I’m sorry if I’m out of format.
Recently, I was rummaging through my gear collection looking for some extra stuff to put up for sale and found that I had a 4-pack of Amplifier Tubes laying around.
I had taken a newly acquired Fender Twin Reverb (1972-1976) in for servicing about 2 years ago (the previous owner had added a wattage modifier switch that caused instability in the circuit, but no issues with the tubes). It took a while to hear back from the amp tech, but he eventually reached out and said he had not only repaired the circuit, but replaced the tubes because he didn’t believe the quad had ever been taken out. He sent them back in a wrapping for me to take a look at.
I believe they are a set of 4 black-plate matched 6L6GC tubes serial numbered 7439. Though, I could be wrong. There’s barely any information online that I understand. There appears to be more writing on the glass of the tubes that has faded from time.
I’m not sure what sort of quality I’ve stumbled across here, but any tips or advice on what I’ve got would be much appreciated. I am NOT looking to sell and this is not a post trying to advertise.