Since the 19th century, art historians have debated which passages are attributable to the obscure Hubert and which are by Jan, famous across Europe by the early 1430s. In the 17th and 18th centuries, it was often assumed that Jan had found a number of random panels left behind after Hubert's death and assembled them into the current format. This view has been discounted since the early 19th century, on the basis of the obvious overall design of the work, although there are obvious stylistic differences between many passages.