The Nagel Bikes were built between 1984 and 1988 in the former DDR (Deutsche Demokratische Republik or German Democratic Republic) before it was re-united to western Germany in 1989.
A Trials bike enthusiast, Thanheiser regularly restores classic trials bikes, going to the extent of reproducing the original paint work and stickers, based on documentation and original photos.
He runs a constant classified advertisement in Germans trialsport magazines, looking for oldschool trial bikes.
This one is quite unique, maybe the only such bike left today.
Photos from Thanheiser - www.thanheiser.net