These are 80's Chinese 12ax7. Mesa used them in the early 90's I believe. I really like them, I use them in my Mark III black stripe.
Same as these: http://www.dougstubes.com/nos-chinese-12ax7-80-s-90-s.html
Well apparently according to Mesa, Hetfield used a IIC+ Coliseum: https://www.facebook.com/MesaBoogie/posts/10153929582297685?comment_id=10153929727717685