Re:
We see a lot of old Alu-Rads around Vienna many clearly abandoned which is either a testament to their quality or their current undesirability (there's no retro scene here).
I too have a red Alu Rad Edition, in fact, I got it from my good friend Brancaleone (above). Yes, it's very heavy but it's an amazing bike and to think it was from a period when the only mountain bikes you could buy in Europe were from Muddy Fox or Dawes and possibly Peugeot but this bike is aluminium. The Alu-Rads I've seen are very similar with full mudguards, racks and dynamo/light combo's so they weren't designed to be light off-road bikes. I'd say they were more aimed at rugged out-doorsy leisure use and being German you kind of get the feeling that the thought process was along the lines of other great German kult items such as VW Beetle, Unimog, Haflinger, etc. So, not really designed for a specific use but more of a utilitarian lifestyle/statement. Kettler didn't follow a trend because there was no trend.
The other thing with these bikes is Kettler didn't give much choice, they were all green except the red Edition model and the odd rare girls models. they were all the same size which explains the sliding seatpost that you see. They all came with the same stem, mudguards, lights, chainguards etc.
They were high quality with alloy lugged frames and as Brancaleone points out Kettler fitted a lot of their own branded parts like headsets, seat, racks etc plus some Kettler touches eg the red large cog at the rear, the rear derailleur guard and the colour-matched bars, rack and stem. They were fitted with a range of Shimano parts but no two bikes had the same parts, it was almost as if there was a huge box of miscellaneous parts to work through. The ones I've seen come fitted with EZ shifters, Sport cantilevers and 9-finger levers and early 84/85 Biopace cranks but I've also seen Deere head parts, Deore II parts plus Exage on some of the later bikes. Interestingly, the design of the bikes didn't change for ten years even the very basic graphics. It was like the Henry Ford mantra that you could buy our cars in any colour you want just so long as it was battleship green.
Here are some Alu-Rads I've seen around Vienna in various states of abandonment starting with my own red Edition which I'm toying with fitting with cream tyres.