This is a U.S.A. made unused Seth Thomas Tradmark Double end clock key, one side is for winding the clock up and the other is for adjusting the time.
This key will fit your antique Seth Thomas mantle clock with #124 and #120 movements.
This key will not fit Seth Thomas clocks with German movements or Seth Thomas clocks that have #89 stamped into the back plate of the movement. Seth Thomas clocks with German movements in them need my Hermle #7 key, and clocks that have movements stamped #89 need my Seth Thomas #6/0000 key.
This key is a #4/0000
This key is American scale.
Check out our
key size chart.