Hey guys, did alot of googling & can't find a good answer so maybe you can help. A couple weeks ago I bought a 1984 Marshall 4212 combo. I wanted to retube it so I went to the tube depot site & when you punch in that amp it comes up with 5 ECC83s and 2 EL34s. ECC83s look right but I'm not sure on the EL34's. Ones in the amp do not have a single mark or number anywhere (and I've went over them with a magnifying glass lol) and they're what I would call "bell shaped". Would these be 6550's?