This is a clone of Stephenson's Adder. It is probably made of nickel-plated brass (it is not magnetic, except for the six rivets and the pawl axle). On the back is stamped the text "CIN SPECIALTY MFG. Co., M'F'RS, CINCINNATI, O". It was probably made somewhere between 1910 and 1914 and sold using the names "Perfection Adding Machine" and "Perfection Pocket Adding Machine". It is virtually identical to Stephenson's adder. Even the decoration on the front is the same as some Stephenson's adders except for the spot at the top left corner where the axle for the ratchet pawl is located.
Dials don't spin freely. May need some WD40. Still a great collectible!