Philips codes before 1934:

Compiled by Frank Philipse. The old Philips tube code consists of a letter followed by 2 or more digits and sometimes a suffix letter.

1st letter gives heater current.

A - 0.06 to 0.10 A
B - 0.10 to 0.20 A
C - 0.20 to 0.40 A
D - 0.40 to 0.70 A
E - 0.70 to 1.25 A
F - higher than 1.25 A

2nd digit or 2nd+3rd digits gives the heather voltage.

x - heater voltage < 10 V
xx - heater voltage >= 10V

The last 2 digits give the type of device in the tube.

xx - amplification factor for triodes
41, 51 etc - tetrode with spacecharge grid (2nd grid is control grid)
42, 52 etc - tetrode with screen grid (1st grid is control grid)
43, 53 etc - power pentode
44, 54 etc - triode with diode or tetrode with diode
45, 55 etc - hf tetrode with variable gain
46, 56 etc - hf pentode
47, 57 etc - hf pentode with variable gain
48, 58 etc - hexode frequency changer
49, 59 etc - hexode with variable gain

The suffix letter gives additional information about the tube.

H - ?
N - New, later version
S - Special, enhanced type
T - ?

Examples

E499 - triode, If=1A , Vf=4V, gain=99
F443N - power pentode, If=2A, Vf=4V
B2046 - hf pentode, If=0.18A, Vf=20V