Eugen Allmendinger full-carbon prototype derailleur

105g! The headline news about this brandless, generally anonymous object is that, at 105g, it is the lightest derailleur in this collection.

I know very little for certain about it. However I have a number of, slightly vague, beliefs about it, as follows:

It was probably created by Eugen Allmendinger, a prolific patenter of designs for bicycle parts, in the town of Biberach, in southern Germany.
It may have been sold by a company called Bike-Tuning-Parts (BTP), owned by Bernhard Langerbein, in Hamm in the Ruhr. Similar derailleurs were sometimes referred to as 'BTP' derailleurs.
Another company, possibly called Carbon Crew may also have sold these derailleurs - or been involved in some way. You sometimes see references to 'Carbon Crew' derailleurs.
At some point in the early 'noughties' Eugen Allmendinger started to work with Lightweight, and this design formed the starting point from which the Lightweight derailleur was developed.

I have not used this derailleur in anger, but to my eye it looks rather fragile and slightly inaccurately made. I can see why Lightweight reworked and professionalised the design. I can also see why they let the weight rise marginally to 120g for their production model.

The adjustment screws look very odd but may be original. I have seen photos of other examples which have these incongruous screws. But who knows exactly what is original on a near-one-off like this - perhaps only Eugen Allmendinger himself.