Hamilton mantel clock - gladwyn 1977?

inherited piece that I want to work. chimes work, but clock isn't. I have original tags, but that info doesn't help bc the clock mechanisms just don't work. have had it about 13 years on top shelf of a closet. Have tried the turning it left and right gently, and a little less than gently, but not harshly. Could it be a matter of dust inside? looks clean. Also... I remember my grandmother had two clocks, and this one she had taken for repairs.