[Maarten]

The first two digits are called "code group" and started out corresponding to a main industry group or industry group so they indicate the kind of product the number refers to.

The interpretation of the remaining 10 digits is determined by the code group, even though the meaning is relatively consistent between code groups.

Code groups 01 through 82 mostly follow the same pattern, with the exception of 48 and 53. Code groups from 85 through 98 are commercial numbers, what we would call SKU's in modern jargon and may or may not follow similar patterns.

Most relevant for this forum are code groups
31 for consumer electronics (originally main industry group "radio, gramophone and television")
35 for telecom
39 for electro acoustics
40 for professional electronics
42 for appliances and large appliances
46 (later) for large appliances

48 and 53 for service parts (not an industry group but straight under the core organisation)

85 (later) for large appliances
86 and 90 for consumer electronics
88 for appliances and large appliances
95 for telecom