Full Details

Name and Model Number Appoullot T2 and T3 LogZ
Spiral Slide Rules
Country of Origin France
Date of Manufacture c. 1930s
Front Scales C, L, 3 revolution number scale, special root scales, tangent & sine scales. Scales wrap in a curious artistic way. Outer scales have accessory vernier scales for increased precision.
Back Scales none
Scale Length 3 revolution spiral number scale is about 60 cm long on the T2 model (13 cm diameter disc) and 79 cm long on the T3 model (20 cm diameter disc).
Type of Rule Disc
Construction 13 cm diameter (Model T2) & 20 cm diameter (Model T3) irregularly shaped enameled aluminum discs, with two transparent celluloid cursors. Fitted leather cases.
Area of Use Generic
Comment Also produced in as a larger Model T4 with a 140 cm long spiral on a 30 cm diameter disk. Curious artistic arrangements of scales with a spiral scale jumping another scale. Cursors also have curious shapes. I have instructions (176 pages) by L. Appoullot copyrighted 1931, entitled: La methode du LOGZ par L'Inventeur du LOGZ. (The method of LOGZ by The Inventor of LOGZ.) I also have sales literature promoting the LOGZs as "Ateliers de Précision" (Workshops of accuracy)

Rarity RRR
Donor Collection of Ed Chamberlain
Match Number 153
(Click Picture for Details)

In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.