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Charpentier Calculator - Calculimetre G. Charpentier

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The Charpentier is a beautiful example of a circular slide rule dating from approximately 1882. A nickel plated metal body with a log scale along its outer diameter holds a brass inner ring also stamped with a log scale that rotates along with the cursor arm. The forked pointer is fixed to the brass ring via rivets and thus also rotates with the cursor arm.
 

 
 Though Charpentier is French for 'carpenter', this rule was not necessarily intended for tradesmen, rather the inventor was Monsieur G. Charpentier.
 

   
British Patent 2119 was provisionally granted in 1882 to A. J. Boult for G. Charpentier with the title "Slide Rule and Computing Scale." 
 

 
Here is a nice photo of another example:
 
In some instances, the calculimetre is also stamped with the mark of Keuffel & Esser Co. of New York and Chicago, and K&E acted as an importing agent and distributor. Below is a reference from the 1895 Keuffel & Esser catalog
 

  

 
 
 
 
 
Above and below is a most unusual Charpentier in its original case
Here the forked pointer of the classic Charpentier is replaced by a solid radial cursor attached
to the fob, and this cursor has a single rivet attachment to the brass inner ring.
(source ebay.fr)
 
The reverse has a stubbed radial cursor attached to the fob.
The diameter of this unusual piece is the standard size of 6cm.
(source ebay.fr)
The original case (source ebay.fr)
 
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