WWII US Army M17 Artillery Telescope, Elbow

about 1 foot long and 6" tall....weighs about 6 pounds....sight focus works properly but sticky with WWII grease....lens filter selector works smoothly with clear, neutral, amber, red....neutral/amber optics appear dusty, internals could be cleaned of dust for perfection....attractive original finish of dark olive drab case, gloss black optics and clean metal dataplate....from personal collection, on display last 40 years -5