Need help IDing an (NOS?) tube..

[fromthebark]

Did a lot of searching and didn't really find much.. so far I THINK they are RCA NOS - They're definitely not new..
my Mesa Express 5:50 had a bad 6L6 and kept blowing it's fuse, my friend had these so I popped them in and it works fine, and now actually sounds a hell of a lot more vintage than it should, almost tweedy, even on the BURN channel, which should be almost rectifier territory. I was quite surprised they worked to be honest, and I really dig the sound. I want to sell the amp so I needed to get it working again and these seem to be posing no problems thus far. I played for a good hour and really enjoyed the very different sounds compared to the Mesa tubes that were in there before.

It's a 6V6GT, the glass is painted black on the inside, you can see through if you REALLY try - both tubes say Grade [27] and Batch [52/08] hand written, and are stamped in white with 6V6GT - no other ID markings that I can see.

Here's a couple pics.

 

[fromthebark]

also trying to decide whether to put it up on Ebay with these in it, or spring for some mesa 6L6's to sell it with, since the person who's looking to buy an Express 5:50 probably wants the typical sound of an Express 5:50. These made it sound like a different amp completely.

 

[unix-guy]

While I am no tube expert, I don't think running a 6v6 where a 6L6 is normally used is going to be good for the tubes

Doing a quick Google search for "swap 6v6 for 6l6" has some interesting info...

I'd expect at a minimum that the tubes will have a shorter than expected life

 

[fromthebark]

Well I didn't worry too much about it because of Mesa's fixed bias thing they have going on.. I'll probably end up grabbing a pair of mesa 6L6's from sweetwater, but I still want to know what the heck these tubes are.