Thanks Vince
Your link has allowed me to check the cover pictures, and the "headline" contents, but no joy. That's a very useful site for checking the LGB models included in each catalogue (by allowing you to download PDF copyies). Unfortunately the "Depesche" section douesn't provide any downloads, just images of the front covers. Thanks for trying to help, though.
In case anyone out there has some oldish Depesche magazines, the edition I'm looking for (or even to identify) is the one where advice was offered for converting an LGB 2090 4-wheel diesel into a 6-wheel HF130 type diesel (sometime before LGB brought out their own HF130 models in 2005). I have acquired one such conversion, and have found a reference to it on a German forum in 2007, saying (translation by Google) “based on an old plan in the LGB Depesche from the small, originally 2-axle LGB diesel locomotive” and “HF diesel in connection Kistenfabrik (the locomotive is a conversion of my father from the small two-axle LGB locomotive, after an older LGB-Depesche)”.
All the best
David