Library Hunt @ DTU

I do like bing and co in normal day live but I hope that it will not be of any help solving this mystery. I have to admit that I have not been able to accomplish this through asking questions the web can't answer but I hope that I have found a solution.
PLEASE remember that you are in a library during parts of the cache! Keep the noise down.

A) What is the number of the object above the chess board?
B) There is a peace of art you will have seen by now. How many spikes does it have?

In order to answer the following questions you will first have to find the Brockhaus, 19th edition from 1986 to 1996.

C) How many circular sky-holes (windows in the roof) are in this room?

D) In the Brockhaus you will need to find an instrument that can be described as follows: The instrument in question is a calculating tool most of you will have used at some time or another. Most modern versions are made out of wood with some sort of sphere (often beans) sliding on wires or wooden roads. There are many different version of this calculator. Some can only be used for little more then adding numbers, where others can be used for more complex calculations at high speed. The Chinese version of this machine can even be used for decimal as well as hexadecimal calculations. There are four pictures associated with this device, all showing a given number. Note the four numbers along with the specific names of the shown device.
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