Traditionally, Seth Thomas clocks are set from the front by using the key that originally came with the clock. By default, the pendulum will swing at an even pace when placed in the correct position.
If the pendulum swings too quickly or too slowly, adjust its pace from the front by either turning the key to the right for a faster pace or to the left for a slower pace. A full turn will make the difference of two minutes in a 24-hour period. If the key is missing, the pace can also be adjusted from the back by raising and lowering the pendulum's ball.
To set the correct strike, start the minute hand at the 12 o'clock position before moving it to either the 9 o'clock position or the 6 o'clock position. This differs between models. Continue that motion until the correct hour has been struck.