Dirk Baldringer has a good reputation for modding Marshalls. He did mod amps for some bigger German acts and the heads tuned by him have a good resale value compared to other modded Marshalls.
I would expect that he did mostly custom orders, very likely you can judge your friends amp only by hearing exactly that amp. But if you want to hear some Baldringer sound in general you have to listen to some older live footage from "BAP" or "Die Toten Hosen" IIRC they were equipped 100% Baldringer.
