Winged C labeling ?

[phil b]

I've seen some EL34s that have an 1004 written on the tubes and others that have 12 11 on them. Is that a date code or something that even matters?
I dont know much about these so any info is appreciated! Thanks.

 

[Scumback Speakers]

I thought the important part was that they were brown bases, so I'm not sure what the codes mean. Sorry.

 

[psychodave]

Likely date codes. You have to look at the tube structure, the place spacers, the getters and how they are mounted. The heat shields, etc.