I did more digging and found the other GE tube, so what I have are pairs, most likely matched. I say that because I've always bought them that way and they are in branded pairs.
So, on the block are:
-two Russian 5u3c (5u4g), both marked with Winged C, but one also marked Sovtek (they are not identical bottles, but the innards look identical)
-two RCA 5u4gb
-two GE 5u4gb
To be honest, I don't remember where I bought any of these tubes, but I try to stay with reliable vendors (e.g. Jim McShane, Antique Electronic Supply, etc). I'll stand behind them if there is a problem. I cannot test them and I can't even try them out. I must have mistakenly bought all these tubes at the same time as I have never had an application for any of them.
I guess that's the price one pays for working in dim light.
