All German bulbs you listed above (Giesemann, Ushio, Aqualine Aqua Buschke, Aqua Connect) show "made in Germany" printed on the outer jacket, but have different arc tube shapes and most of them don't have anything printed on their arc tubes. They don't even look like the ones you showed from Giesemann, but are all very different. Ushio has a precision formed arc tube, Aqua Connect has a straight wall arc tube construction, etc. They also suggest different ballasts to run, so they shouldn't have the exact same gas composition independent of the approximate Kelvin number printed on the boxes (which we should agree that are just "brand numbers").
If you look at the 250W SE German bulbs you have:
Ushio 10K M58
BLV 10K M80
AB 10K M138
Giesemann 10K M80
The suggestion you posted about looking for the printed numbers on the arc tube because they are "all from one source (BLV)" isn't accurate simply because they aren't the same at all.