Brimar type designation system

For example: 13D5
1st letter construction
1 half-wave rectifiers
2 diode
3 triode, output
4 triode, high-mu
5 tetrode, straight
6 tetrode, vari-mu
7 power or video pentode
8 pentode, R.F. straight
9 pentode, R.F. vari-mu
10 duodiode
11 duodiode-triode
12 duodiode-pentode (AF)
13 duotriode, high-mu
14 duotriode for class B output
15 heptode
16 triode for DC coupled outputs
17 duodiode-pentode (RF)
18 triode-pentode
19 ?
20 triode-hexode/heptode


next letter heater
A 3.6-4.4 V indirectly
B 2 V directly
C other directly then 2 or 4 V
D all other heater ratings indirectly heated other then 4 V