In my reply above...my mistake was assuming the non DSP amps were like the DSP amps. It's the DSP amps that were used in 3 different models (e38/e39/e53)...it appears the non DSP amps are model specific.
If you click the following link...you will see that the e38/e39/e53 share the same "uncoded" DSP amps...and over the production run from 1995-2006...there were multiple brands...Lear & Alpine come to mind, I forget the 3rd brand name:
RealOEM.com - Part Search
Sorry for any confusion my previous comment caused.