I have recently acquired a Seth Thomas regulator mechanical clock which has a second hand. The hour and minute hands work well. The second hand doesn’t move and is not stuck. Not sure what is wrong. Not finding anything on the internet that addresses this problem. Am I missing a clutch and spring?
My experience with the older ST regulators, has the second hand directly mounted to the escapement wheel shaft. Just like the newer hermle movements for GF clocks, the second hand shaft is split to fit snugly on the shaft. Check the back of the second hand shaft on the hand, you may need to tighten it up a little with a pair of needle nose. I bet it is just slipping on the shaft. If the clock is running, then the EW is turning. Good luck!