The masterpieces are linked to the organisation of crafts in Europe since the Middle Ages : they were an essential stage in becoming a master-craftsman, or being admitted as a "compagnon", or apprentice craftsman.
The development of craft guilds and corporations encouraged new standards of quality, which found concrete expression in the execution of a masterpiece.
The spirit of the system of "compagnons", based on disinterestedness, means that these works remained anonymous and attribution is therefore difficult. 
Even today art school students demonstrate their talent at the end of their studies by building a scale model.

Here are some masterpieces from the collection
(for detailed information about an object, click once on the image with the left-hand button of the mouse)