 One possible explanation for this change in the pattern of production and hoarding is that it came to be the rule, after the 1030s, that only payments to the crown had to be in the current type, whereas other types of English coinage were viable for other purposes.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.