In the sunken wreck of the "Mary Rose", arrow sheaves were found to hold arrows in lots of 24. Ergo, it seems logical to assume that since Medieval times, arrows were counted by dozens.

An English longbowman was expected to be able to fire 12 arrows in one minute's time when facing a massed enemy. I remember reading about one 'Champion' from the time who would do so (12 shots/minute) and hit a 2'x2' target at 50 paces with every shot while shooting a longbow.

Alot of information from olden times seems to revolve around the number "12" when talking about arrows...

BP