I ran across a few old tubes while going through some old boxes of electronics... have no idea what they're for? There is set of 4 Sylvania 12AX7WA that all have the exact same markings and numbers on them. A couple more differently marked Sylvanias of the same type, a couple of longer, skinnier NEC 6AQ5. They all look clear, but I gather that doesn't necessarily mean they are good from what I'm gathering? They weren't in boxes so that makes me a little suspicious. Anyway, I'd appreciate any advice on how to confirm if these are good. Thanks!