Fefnir Garzog was a famous dwarven accountant. He was also known for being a control freak of epic proportions. He oversaw the books of the Garzog clan with its myriad assortment of mines, refineries, and forges.
As Fefnir grew older, and the clan grew larger, he found himself unable to personally oversee all of the accounting required to keep the clan's books in order. Concerned that the younger dwarves employed under him might not have the mathematical acumen to properly log debits and credits he had a supply of magical quills constructed.
The quill looks like most quills of the type used by an accountant. They are rather drab in appearance, made from common feathers without any special adornment (Fefnir did not believe in wasting money on beautifying common tools). If a detect magic spell is used they radiate a very minor level of alteration magic.
Primary power: The quills store the last 24 hours of use within themselves. This allows them to ‘check the math’ of anyone using them for accounting tasks. They operate in such a way that any errors of an accountancy nature cause the user to immediately feel ill until they correct their math. One side effect of this power is that if someone uses the same quill between ledgers and accounts (mixed book use) they will find themselves set upon by an intense feeling of nausea due to the quill's attempt at reconciling transactions from mismatched accounts.
The quill does not fix errors, it simply makes the user feel ill until they fix the error. Along with being a control freak Fefnir also had a slight masochistic streak.
Secondary power: Upon dropping the quill into a jar of red ink and uttering the command word “audit” in dwarven the quill can be commanded to write anything it has been used to write within its last 24 hours of use. Keep in mind that this is use time, not real time. If a quill has not been used for 100 years it will still retain the last 24 hours of use within it and be able to call such writing forth.
A quill can be reset (erasing all of its internal memory) by placing it in an empty ink pot and uttering the command word “reconciliation complete” in dwarven. This resets the quill completely and allows it to be used with a new ledger.
Notes: When used for writing other than accounting it does retain the 24 hour usage information but does not cause any discomfort unless it detects a math error. As such these quills have been used to spy on the writings of diplomats and underlings. Due to the audit function being limited to red ink its value in creating copies of written works is useful for record keeping but not so much for publishing prospects.