According to an ex-Philips guy :-
"The first digit identifies the type of component which helps when looking at the pcb layout diagram rather than the schematic.
1000 Misc (Switch, connector etc)
2000 Capacitor
3000 Resistor
4000 Jumper
5000 Coil, Relay or Transformer
6000 Diode
7000 Transistor or IC
8000 ?
9000 ?
The second digit refers to the pcb. All the components on the same board start in the same range, for example
1) if a tuner board is 1, the capacitor numbering starts at 2101, the resistors start at 3101 etc,
2) if a front board is 4, the switch numbering starts at 1401, coils at 5401 and IC's 7401 etc.
The last two digits are incremental (the second digit can change if there are more than 99 components of the same type)."