BRIMAR VALVE TYPE & DATE CODES - HOW TO INTERPRET THEM

Well, we did Mullard last week so this time, lets look at the Brimar type and date codes, oft seen on valve envelopes in minuscule inked print, but what do they mean?

Brimar codes come in two parts separated by a forward slash "/".

The first part, of format number-letter-number is the date code where the first number signifies production week of month, the following letter signifies the production month and the second number signifies the production year.

First number: -

1 = week 1 of production month

2 = week 2 of production month

3 = week 3 of production month

4 = week 4 of production month

5 = week 5 of production month

Following letter: -

A = January

B = February

C = March

D = April

E = May 

F = June

G = July

H = August

I = September

J = October

K= November

L = December

Second number: -

1 = 1961, 1971

2 = 1962, 1972

3 = 1963, 1973

4 = 1954, 1964

5 = 1955, 1965

6 = 1956, 1966

7 = 1957, 1967

8 = 1958, 1968

9 = 1959, 1969

10 = 1960, 1970

Moving onto the second part of the code, this is the valve type designator  and can be a three or four digit number with three digit signifying pre - 1960 production and four digit signifying post - 1960 production.  Interestingly, the fourth digit can also signify the Brimar production site but I do not have a verified listing for this.  Accordingly, we have produced the handy table below to use for common Brimar audio devices: -

 So, putting all the above into practice, lets take the code on the rather pretty Brimar 12AT7 ( stock no D302) that I have in front of me.   As you can see from my photo, the code presents as 3J7/565 which translates as an ECC81 produced  third week of October 1957