The keys themselves, and all original drawings of them, have been lost.
According to his gallery, he has made 7,000 original drawings.
Some years later, the three original drawings were destroyed by fire.
About 95 percent of the original drawings were found, with 1,100 scanned by 1993, and a further 140 in 2001.
All they have to do is go back and look at the original drawings.
The original drawing was in his possession during he wrote the description.
Includes original drawings where the power of images is evident.
The virtual model looks very similar to the original structural drawing.
A large number of his original drawings are in the Berlin print room.
Artists also get back their original drawings, which can be sold to collectors.
