 Remarkably little written evidence survives to help numismatists and historians understand how the coinage and its system of changes of type actually functioned.Domesday Book does record that moneyers at certain mints had to go to London to purchase new dies for twenty shillings "quando moneta vertebatur" ('when the coinage was changed'), and that certain towns paid annual sums to the king for the privilege of running a mint.At several towns bishops and abbots had rights to the profits of one or more moneyers (which normally went to the king), but these are no longer reflected by any changes in the design of the coins.