Tavernier-Gravet “Système Audéoud”

Data:

• For financial calculations
• Marked “No.3.”, “Tavernier-Gravet Succ^r  Rue de Babylone, Paris”, “Breveté S.G.D.G”
• 36 cm long, twice as thick and wide as a normal Tavernier-Gravet
• Slide front: 1 year = 360 days
• Slide back: 1 year = 365 days
• Not found in catalogs, CNAM museum etc.
• French Patent 98247, Feb. 1873
• More images at reglacalcul.com

Question:

1. Is this a prototype, or is it produced in any quantities?
   The inventor is probably Paul Jules Audéoud (* 1836-09-10, † 1885-04-02), a mining engineer, banker and collector. After his death, lots of clocks and a calculating disk from his collection were bequeathed to the CNAM Andries de Man
   During the 1873 Vienna World's Fair, Jules Audéoud, rue Saint-Pétersbourg 27, Paris, exhibited a “Spécimen de règle à calcul”. See Exposition Universelle de Vienne, 1873, p.414. At the 1878 Exposition Universelle Internationale in Paris, J. Audéoud, rue de Hambourg 15, Paris, exhibited a “Règle à calcul”. See Exposition Universelle Internationale - Catalogue officiel Section française: France, groupes II à VI, classes 6 à 68 · Volume 2, Paris, 1878 p.21. The fact the slide rule was displayed under Audéoud's name, and not Tavernier-Gravet, might indicate it was never produced and sold commercially. Andries de Man
   
2. Is it useful?
   Financial calculations often required long scale instruments, like the LOGA drum, see e.g. Nico Smallenburg, “Financial calculations with a LOGA 15mZ calculator”, MIR 96 p.11-16 Chris Hakkaart