Here is a link to Tube Classics that gives descriptions of the various EL84's, hope this helps.
http://www.tube-classics.de/TC/Tubes/Valvo%20EL84/EL84.htm
http://www.tube-classics.de/TC/Tubes/Valvo%20EL84/EL84.htm
Very early Mullard EL84s with O-getters?
I have two coin-based O-getter EL84s, with no holes in the plates. One tube is branded El-Menco and the other is branded Siemens. The El-Menco shows "Gt Britain" and "164-519" in white print. There are no etched production codes visible on either tube.
My limited understanding is that the earliest Mullard EL84s had coin bases and a "1608" designation (pre rX1). There were a few different factory codes, all indicating 1954 as the year of manufacture. At least some of those tubes (F4 factory code), had no holes in the plate.
The coin base would suggest very early production, but the O-getter, as opposed to disc or square, seems inconsistent with that. Thanks for any helpful comments.
My limited understanding is that the earliest Mullard EL84s had coin bases and a "1608" designation (pre rX1). There were a few different factory codes, all indicating 1954 as the year of manufacture. At least some of those tubes (F4 factory code), had no holes in the plate.
The coin base would suggest very early production, but the O-getter, as opposed to disc or square, seems inconsistent with that. Thanks for any helpful comments.