Every "Forestville Eureka" style clock I've seen had missing parts. Obviously there are some working models extant but I suspect most were repaired by using parts from "donor" clocks; thus those seen in need of parts.
Does yours have a UL sticker? As noted by many, most of them designed for utility mains power "fried" the transformer. The company went out of business in 1979 after converting some of the clocks to battery operation.
There is a lot of textual information on the message board from years past about the "Forestville Eureka." Use the Search Function to see what others have said about their experience with the clock.