Based upon the getter itself comparing it to some GT12AX7's they appear to be Chinese because the 12AX7's have the additional metal stabilizer that are known to be in Chinese 12AX7 tubes. It very well could be that they are Chinese because the 420 was a Chinese tube that Mesa used and I am assuming that these tubes were bought around the same time because the amp they came out of has sat for years unplayed. There is actually one that though matched to one with the washboard looking plates has a heavy ring getter. I am assuming that the pairing may have been made at a transitional time in manufacture/batches by Mesa.
Just out of curiosity I pulled out some older EL34M's that I have and they are identical getters. Now that makes me believe that the whole getter construction idea is out the window unless the EL34M's that I have are actually Chinese. They could be anything though because I didn't buy the EL34M's. I received them in an amp and I kept the good pair of the quad when one went south. When I had the amp retubed and rebiased for the new set of tubes (Marshall amp) I just asked that the amp sound the same when it came back. It was outfitted with E34L-CZ's when it returned. It sounded as far as I could tell at the time the same. This throws everything for a loop.
Now, I really need these tubes identified because it is making me question my thoughts on certain tubes. I mean I know some decent tubes came out of China but then again some of the stuff was pretty shoddy. I am just wondering if I inadvertently sold some amps over the years because of a tech not picking tubes that agreed with my ears. I know that the 420 sounds great for a 6L6 and that it came out of China. I am just wondering how many Chinese EL34's had as good of standing amongst their peers. I am aware that the STR-EL34B is a good EL34 but I was under the impression that there hadn't really been any great Chinese tubes in general. Maybe it was a discriminatory thing on behalf of my tech? I dunno, I am beginning to rethink things now. The general concensus is that Chinese tubes suck. There again, Mesa has been choosing to use them for quite a while, not that I care for some of Mesa's choices.