Tavernier-Gravet “Système Audéoud”

Data:

• For financial calculations
• Marked No.3.
• 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? Is it useful?
   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
   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