This treasure is a G. N. Mindling Adder in steel with Nickel Plating Adder Calculator with stylus (Stylus may not be original, but works very well).   It is the very early model as back does NOT have Mindling stamp (the transition between Stephenson and Mindling).   Later more common models had the Mindling stamp on backside.   Calculator is in excellent condition with tens carry over.   It is an unauthorized copy of the Stephenson adder, calculator that dates to late 1890s to early 1900s.  These little adders were popular for shoppers.   The original model Stephenson model is pictured and described in the book “Antique Office Machines” by Thomas Russo.  It is called a small cogged disk adder of the Pascal Principle.  The front has a decorative trim around the two disks with 10s carry over.  This rare and seldom found treasure is in very good condition with light pitting and operational (Calculates 1 to 99 with 10s carry over).  There is slight wear on Nickel plating, but still in beautiful operating and display condition.   Size is 3.5” x 2”.   This will highlight any old calculator collection.