The EL84 tube was developed in 1953 by Phillips, and is best known for it's usage in British amplifiers, such as Vox.
The EL84 vacuum tube is a power tube that is very unique in that it uses a 9 pin socket (the same as a 12AX7). This tube is almost like a smaller version of an EL34.
Genalex Gold Lion EL84/N709
JJ EL84 / 6BQ5
Tung-Sol 7189 / EL84 / 6BQ5