Keuffel & Esser K & E Optical Alignment Scope

This is a Keuffel & Esser K & E Optical Alignment Scope Collimator. Specifications: -Barrel length: 12″ -Barrel Diameter: 2″ -s/n 181959. Note: Possible model number 71-4010 / P-1660 (unable to confirm number – not on unit)