Deciphering European tube date codes

A lot of questions have been asked about when a tube is made, so here you go, a quick guide on how to decipher the date codes.

For the most European tubes made after 1955 date codes are located on the bottom of a side wall of a tube (not always the case)
Location of tube date code
In this case it’s B0D (this is for Mullard, Blackburn – 1960 – April)

The code is broken down into 3 or 4 characters. 1) Factory code , 2) Year of Manufacturing, 3) Month, 4) Week (this is usually on tubes manufactured after 1960)

The first 2 characters are the most important ones since factory code would show where a tube was made and year, well, this one is super important since sound changes quite a bit for the same tube from the same place depending on a year. For 3 character codes 8 means 1958, for 4 character codes, 8 means either 1968 or 1978 (that depends on change code – more about that later).

Finding the code could be very easy, but occasionally it’s quite challenging. Start with naked eye and if you can’t find it use magnifying glass. Date codes are usually done with acid, so they are burned into glass. Some tubes, like Telefunken, don’t have acid date code, it’s usually printed on the glass as part of the silk screen and very easily removed.

Most popular factory codes:

Code Manufacturer Location
B Mullard Blackburn, Great Britain
C Hendon Works Alberton, Australia
D Valvo Hamburg, Germany
F La Radiotechnique Suresnes, France
G Mullard Fleetwood, Great Britain
J Mullard Tottenham, Great Britain
L Mazda Bruxelles, France
N Matsushita Takatsuki, Japan
n Matsushita Kyoto, Japan
R Mullard Mitcham, Great Britain
r Philips Ontario, Canada
V Bharat Electronics Bangalore, India
X Philips Sittard, Holland
x Philips Chile
Y Philips Sittard, Holland
+ Philips Sittard, Holland
Y Philips Sittard, Holland
= La Radiotechnique Cinchy, France
* Amperex New York, USA
± La Radiotechnique Chartres, France
Siemens Munchen, Germany
 Delta sing Philips Heerlen, Holland
circle and dot sing Ei Nis, Yugoslavia

Month codes are quite straight forward:

  • A – January
  • B – February
  • C – March
  • D – April
  • E– May
  • F – June
  • G – July
  • H – August
  • I – September
  • J – October
  • K – November
  • L – December

Next step would be consider which Change Code the tube has been developed under. That’s the 3 character code above Date code. Usually looks like I61, etc. This is much more complicated since there is no standardization on that, each factory used their own codes.

Some most popular change codes for ECC83 (dates are very approximate):

  • Mullard
    • mC1 (Long plates) – 1955-1956
    • F91 (Long plates) – 1957-1958
    • F92 (Long plates) – 1959
    • I61 (Short plates) – 1959-1964
    • I63 (Short plates) – 1965+
  • Siemens
    • mCP – before 1956
    • mC1 – 1956
    • mC5 – ?
    • mC6 – ?
    • I61 – 1961
    • I62 – 1962-1966
    • I63 – 1967-1969
    • I64 – 1970 (end of production)
  • Philips/Amperex
    • mC2 – 1955-1956
    • mCA – 1956-1958
    • mC6 – 1959
    • I61 – 1959-1960
    • I62 – 1961-1962
    • I65 – 1963-1969
    • I66 – 1970-1972

The list goes on and on and on…

So there you go, hopefully some of the mystery is gone from the tube world.

3 thoughts on “Deciphering European tube date codes

  1. There are some European manufacturers that didn’t follow the same date code scheme.

    Tesla – date codes are printed in large letters on glass:
    Tesla Date Codes

    Tungsram – date code is located on aluminum foil that’s inside a tube – general understanding is that the higher the tag is located, the later is production date of a tube.
    Tungsram Date Codes

  2. Bruxelles is not in France. It is in Belgium. You are confusing Mazdas. Mazda France isn’t the only Mazda in this game. You also have Mazda as sold by Ediswan/Brimar/Thorn in England. You also had Mazda/Adzam as sold/branded by M.B.L.E. of Bruxelles, which was bought out by Philips.

    The ‘L’ code is for M.B.L.E., NOT for any of the French factories.

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