It must have been up to the maker as to how he kept his books. Serial number were not even required on guns at that time. What you describe is one maker keeping an order book and another a delivery book. Most kept a delivery book in part to keeping out track of payments to out sourced workers.
In British gun making, the two different books were called either the Ledger or the Cash book.
The Ledger was the book that held guns serial numbers, repair or refurbish work, and other pertinent information pertaining to the gun. The cash book is the book that kept track of outgoing payments to out workers, especially engravers and blackers.
Unfortunately, very few gun making firms have intact cash books. The cash books are interesting in that they can dispell popular myths and rumors....for example....the Sumners exclusively engraved all Boss guns...the Boss cash books have numerous entries of money going out to Thomas Sanders (gun engraver) in Soho.
