Mullard EL34 production codes

This was a post on an amp BBS asking about Mullard EL34 production codes, what they mean, and my response:

I know this has been discussed here before, but I've misplaced my hard copy of how to decipher this. I
have several NOS Mullard EL34's, dark choc. brown bases. Etched codes are as follows:

: xf2 B9H2 
: xf1 B1E2 
: xf1 B1F4 
: xf2 B0L2 
: xf2 B2D3

xf1 coding indicates Mullards made in the Blackburn Works, in the U.K., from the late '50s to the early
'60s. xf2 indicates either the Blackburn Works in the U.K., or Eindhoven, Holland tube factory (after
Philips Electronics bought Mullard in the '60s) The differences in the 2 facilitie's tubes are in the bases -
color and size, and the getters. Both facilities made these tubes for other companies (for rebranding) as
In the case of the 1st letter, ie 'B' for xf2 that's the factory code, xf1=Blackburn, xf2=Blackburn -or-
Eindhoven, Holland. The 9 would be 1969 (in the xf2 case). The 'H' is the date code month -August. (A
= Jan, B = Feb,... H = Aug), and the '2' is another date code, the week. in this case the 2nd week of

In the 'xf1' case the 'B' is Blackburn, the '1' is 1961, the 'E' is May, and '2' is the 2nd week of May.
etc for the other tubes...

This is information I've rcv'd/learned from Vacuum Tube Valley magazine, and also from working for
Philips Electronics - Electron Optics Division (based in Eindhoven, Holland) from 1984 - 1998. -Ron