electric? key wind?
Have you tried a clock/watch repair service? We inherited an old watch with a very colorful and kinda' naughty family history. So off to our local jeweler, who also repairs all kinds of clocks & watches. Well, he opened it up, and in little tiny writing were repair dates. And it is solid gold. And the stories (maybe) could be true, going by the dates. :unsure:
So, do you think your mantel clock might have marks of repair? And you might get an idea of date made, and possible value. PS: best if you don't open the case yourself. KB