For your consideration is this very good ' THATCHERS CYLINDER SLIDE RULE.   Maker is Keuffel & Esser - New York'. ' '  Initially patented in 1881 - this example appears to be a model manufactured in or around 1917.  Contained in it's original mahogany fitted, finger-joined case (excellent condition). Also includes the original Instruction Booklet The case and intrument have matching serial numbers. Rule is 22 inches long - will extend to 35" or more which internal slide extended.  For the condition conscience, this is an excellent example.  These have a tendency toward serious black moisture / age spotting that can, at times, entirely obliterate the rule.  This one has only very slight, light brown spotting confined to approx 4 inches on one end - does not detract at all.  Also the lower instruction column attached at the bottom of the stand is in excellent plus-plus condition.  Rule is perfect working order - slide moves in and out with ease and the whole rule rotates without effort.  Overall a superior example  of one of the most interesting slide rule ever produced....  

 Shipping estimate to US East Coast approx.  $45 - $55. 

 Overseas estimate  $50 - $80 country determined

         Shipping Insurance at buyer's option and cost - Advised