The ledger books (pianos and harps) contain, in addition to the instrument number, interesting information such as:
The Fonds Gaveau-Erard-Pleyel contains several original ledger books, including the earliest ones from the Erard firm. Other ledgers are held in the form of photographs of the originals, ordered by the AXA insurance group prior to the separation of the originals from the archives. The originals of the photographed ledgers are today held by the Musée de la Musique in Paris, along with other ledgers from later periods. The ledgers for harps sold by the London branch of the Erard firm are today held by the Museum of Instruments, at Royal College of Music, London.
The Erard and Pleyel firms kept these ledgers as day-to-day tools, not as research tools for posterity. As a result, answers to musicological questions posed by today's musicologists are often not easy, due to illegible handwriting, erasures, instruments that are bought back and resold or rented out, etc. As is the case for any research project using primary sources, one needs experience and above all patience.
Please note that for most of these ledgers, one reads on a single line continuously across two pages (for example, from the page "Doit" to the facing page "Avoir" in the sales ledgers), but in order to facilitate the reading on the screen, we have chosen to present only a single page at a time.