This older Key-wind Elgin pocketwatch had a broken mainspring.
Looking up the parts data for grade 13 (early one) shows factory number 812, bottle (refill) number 282. This is a really common mainspring for 18 size Elgin pocketwatches.
The Elgin packaging for this spring shows the refill number 282 (the number used in an Elgin parts assortment, and 812 (the factory number).
Note that 838 is an inventory number referring to mainsprings. Most Elgin packaging includes a number, 285, from a different system for this code. See this list... I just happened to pick an oddball for this photo.
Most Elgin springs for 18 size watches will be "hole-end", meaning the end has a hole. It will also have a couple tabs that go into slots in the barrel and the barrel cap.
Older Elgin barrels don't have the slots. A common modification I see is a tab slot filed into the cap for the upper tab, and the spring having the lower tab cut off. It's easy to file that slot in the edge of the cap, but harder to cut the slot in the bottom edge of the barrel, and hole does most of the work of holding the end secure.
Where the barrel does not have a post for the spring end hole, another common modification I see a lot on old key-winds is a hole drilled in the sidewall and a post threaded in, for the hole. Allowing a tabbed hole-end spring to work.
An example of a spring modification is shown here, the lower tab files off. I have several springs sitting around that look like this. I should also mention at this point that sometimes the hole is too small or the wrong shape and the mainspring also has to be modified accordingly - even though it is the "correct" 812 part. You have to have those tiny files handy.
Anyway, when I went to change the spring on this project, I thought this would be the situation.
Many older Elgin key-winds have a "T-end" rather than a hole-end. On these there is no hole, nor tabs, but the tip of the spring is folder back over a small piece of steel wire that sticks out top and bottom like a T.
Elgin manufactured both hole-end and T-end mainsprings, both having part number 812. A common watchmaking task was to alter a mainspring to have the type of end the barrel called for.
With these the end of the spring is fold back and out on itself so that it catches on a ledge in the inside edge of the barrel. This type is common on later "modern" wristwatches from say the 50s and 60s, especially Swiss movements and older European pocketwatches.
If I have ever seen an 18 size Elgin with a tongue-end mainspring, I can't recall it. Weird...
This is the original barrel too, it has the movement serial number stamped inside.
Again, it is certainly possible to create a tongue-end from another type. But a previous repairer did something else to this one. Notice in the image there is a round hole in the bottom edge of the barrel just past the ledge. Someone has drilled a hole there so the more common, from the factory, T-end spring could be fit.
Check this out. The repairer has filed away just part of the the lower tab only, leaving something that would fit in the hole, like it was a T-end spring, and even though there is no post for the hole.
So, some history... At some point the original tongue-end spring broken. Not able to get one like that (no surprise), the watchmaker drilled a hole and used a T-end spring.
When the spring broken again later, probably a different watchmaker altered a regular hole-end Elgin mainspring, the most common type, to work with the hole in the barrel.
By the way, the barrel cap has a notch in the edge intended for inserting a screw driver to remove the cap. In each of these cases that notch can be located to hold the upper tab or T-end.
So what do I do?
1) Alter a mainspring to make it a tongue-end.
2) locate a T-end Elgin spring.
3) Cut a slot and add a post to the barrel.
4) Replace the barrel with a later one.
5) Alter a hole-end spring the way someone other repairer did.
Option 1... I know how to fix a spring end and have done it many times. But to do this, I'd have to use an old steel spring, and it would involve shortening it slightly. In addition, there's good reason they didn't use tongue-end designs. These springs on the big Elgins are pretty strong. And this is a key-wind. I think it would be prone, having no tabs, to coming unhooked. And an older steel spring, unavoidably partially "set" would make that even worse.
2) Locate a T-end spring. This has the advantage of leaving the barrel alone, and not making any permanent modifications. But again, I'd be forced to use an old mainspring, not at its prime. An alloy spring of that end type is probably not available (at least I have never seen one).
3 and 4) Replacing or altering the barrel to match a new alloy spring is a bad way to go. It would be one thing if it was broken or worn out, but it isn't. It's a serial numbered part and should be preserved. Watchmakers' rule: never alter existing parts to make a replacement work.
5) Maybe, but the spring really isn't intended to work that way.
So far so good.
One more interesting thing here. This movement has a different regulator from other grade 3 examples I have seen. Others have the regulator facing back over the balance cock. On this one, the regulator faces out over the top plate. The index is engraved on the plate, unusual for Elgin. They normally used a separate indicator screwed to the plate.
See the entire album for this project here:
https://photos.app.goo.gl/65bEo3JBkxKVehd88
See more "creative repairs" here!
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