Seth Thomas Clock Movement Replacement Guide
How to Find a Replacement Movement for a Seth Thomas Clock
If you have a Seth Thomas clock that needs a replacement movement, do not order a movement based only on the Seth Thomas name on the dial or case.
The name on the clock identifies the clock brand, but the movement inside may need to be identified separately. Depending on the age and model of the clock, you may find an original Seth Thomas movement or a later movement made by another manufacturer.
The most important place to start is the movement itself.
If you already know the movement manufacturer or number, visit our Clock Movement Finder or browse our complete selection of replacement clock movements.
Step 1: Look at the Back of the Movement
Open the rear access door of the clock and look directly at the back plate of the mechanical movement.
Do not rely only on information printed on the clock dial, case label or model tag. What we need is the information stamped into the actual movement.
Look for:
Manufacturer name
Complete movement number
Any additional letters or numbers
Pendulum information
Chime or strike configuration
Take a clear photograph of the entire back plate before removing anything from the clock.
If the markings are difficult to read, take several photos from slightly different angles and under good lighting.
Seth Thomas Clock vs. Seth Thomas Movement
This distinction is extremely important.
A clock branded Seth Thomas does not necessarily mean that a modern replacement movement will also carry the Seth Thomas name.
Over the years, Seth Thomas clocks have appeared with different mechanical movement configurations, and some later clocks used German-made movements. Your existing Seth Thomas inventory provides real examples: Seth Thomas clocks on your site have appeared with Hermle 131-030, 340-020, 350-060 and 791-081 movements.
That is why the number on the movement is generally more useful for replacement purposes than the model name printed on the clock case.
What If My Clock Already Has a Hermle Movement?
If the movement inside your Seth Thomas clock is stamped Hermle or Franz Hermle, identification is usually much more straightforward.
Look for a number such as:
131-030
340-020
350-060
or another Hermle model number stamped into the back plate.
Those numbers identify the movement family and configuration and give you a much better starting point for finding the correct replacement.
You can browse our complete selection of Hermle replacement clock movements.
Do not stop at the first few digits, however. Whenever possible, record the complete number and every additional marking on the movement.
What If I Have an Original Seth Thomas Movement?
Many older Seth Thomas clocks still retain their original American-made movements.
In that situation, searching our inventory for the number stamped on the old movement may not produce an identical movement.
That does not automatically mean that the clock cannot be repaired or that no replacement option exists.
The first question is whether the original movement should be:
Serviced or rebuilt
or
Replaced with a compatible modern movement
For an antique or historically significant Seth Thomas clock, retaining and restoring the original movement may be preferable.
For a later-production clock where reliable daily operation is the goal, a modern replacement may sometimes be the more practical solution.
A qualified clockmaker should evaluate an original movement when preservation or originality is important.
Do Not Buy a Replacement Based on Appearance Alone
Mechanical movements can look extremely similar in photographs while differing in important ways.
Before purchasing a replacement, several specifications may need to be checked.
Movement Number
Record the complete movement number exactly as stamped into the plate.
Hand Shaft
The hand shaft must properly pass through the clock dial and position the hands correctly.
Pendulum
Pendulum-driven movements must be matched to the appropriate pendulum configuration.
Chime or Strike
Determine whether the clock is time-only, time-and-strike, Westminster chime, triple chime, bim-bam or another configuration.
Winding and Drive System
Determine whether the clock is spring-driven, chain-driven or cable-driven.
Physical Configuration
Mounting points, winding arbor positions, dial dimensions and surrounding clock components may also affect whether a replacement is suitable.
For a more detailed explanation of these considerations, read our Replacement Clock Movement Identification & Buying Guide.
Can a Seth Thomas Movement Be Replaced With a Hermle Movement?
In some applications, yes — but not every Seth Thomas movement has a direct Hermle replacement.
Compatible Hermle replacements are available for some Seth Thomas applications, and this is why movement identification must happen before ordering. Emperor itself maintains a Seth Thomas-to-Hermle conversion resource, confirming that compatible Hermle replacements exist for certain Seth Thomas movements.
The important word is compatible.
A movement should not be selected simply because it physically resembles the original or because another Seth Thomas clock used that model.
Two Seth Thomas clocks can require completely different movements.
Examples of Seth Thomas Clocks With Hermle Movements
The relationship between Seth Thomas clocks and Hermle movements is not theoretical. We have handled Seth Thomas clocks fitted with several different Hermle movement families.
For example, our inventory has included:
Seth Thomas Octagon Wall Clock — Hermle 131-030
Seth Thomas Westminster Mantel Clock — Hermle 340-020
Seth Thomas Legacy IV / bracket-style clocks — Hermle 350-060
Seth Thomas Skeleton Clock — Hermle 791-081
These examples demonstrate why there is no single “Seth Thomas replacement movement.” The correct movement depends on the clock and the movement configuration already installed.
What If My Seth Thomas Movement Number Is Discontinued?
Do not assume that a discontinued movement number means you need to find another used movement with the exact same number.
Older clock movements may have been superseded, revised or replaced by later movement designs.
A factory-new replacement, when a compatible one exists, can often make more sense than purchasing another unknown used movement that may already have decades of wear.
The key is identifying the correct modern replacement, not simply finding something with a similar model number.
Should I Repair or Replace My Seth Thomas Movement?
There is no single answer for every clock.
If you have an early Seth Thomas antique with its original movement, restoration may be important to preserving the clock's historical integrity and collector value.
If you have a later mechanical Seth Thomas clock with a replaceable German movement, installing a new movement may provide a practical path to dependable operation.
Consider:
Age and collectibility of the clock
Whether the movement is original
Amount of mechanical wear
Cost of professional rebuilding
Availability of a compatible new movement
Whether originality or everyday reliability is your priority
When in doubt, have the original movement evaluated before discarding it.
Need Help Identifying Your Seth Thomas Movement?
If you are unsure what movement is inside your Seth Thomas clock, send us photos before ordering.
Please include:
A clear photo of the entire back plate
Close-up photos of every stamped number
A photo showing the complete movement installed in the clock
A photo of the clock itself
Photos of the pendulum, weights, chains or cables when applicable
The more of the original setup we can see, the easier it is to narrow down the movement and determine what replacement options may be available.
Contact Just A Clock Collector for movement identification help.
Find Your Replacement Clock Movement
Already have a manufacturer name or movement number?
Use our Clock Movement Finder to start with Hermle, Kieninger, Urgos or Regula, or browse our complete inventory of replacement clock movements.
If you don't know what you have, don't guess. Send us photographs of the movement back plate first and we'll help you determine where to start.