Clocks with a going duration of a year were produced as early as the second half of the 17th century, but they are very uncommon. They were generally timepieces only, as striking mechanisms to go for 365 days at a winding could not easily be accommodated as well as the going train. As it was, the going train of six wheels required a weight of massive proportions. Longcase year clocks look much the same as eight-day clocks from the outside. Only the very robust construction of the movement, the single central winding hole and the size of the weight indicate a year clock.