The Tavole di Biccherna collection consists of 107 works produced over the period from 1258 to the early 18th century, including one copy and one imitation. At the beginning of their long history, these were the covers of the registers of the Biccherna, one of Siena’s oldest and most important financial bodies. Officials of the Biccherna began to commission painters to decorate these covers in 1257 and the practice was then taken up by other Sienese bodies of government and local institutions. As from the halfway through the 15th century, it was no longer covers that were commissioned but authentic paintings, often by the leading Sienese artists.
See: https://www.archivesportaleurope.net/featured-document/-/fed/pk/93131#sthash.ubwJCBag.dpbs
