Job Number 200006, 18 Size Dueber Watch Company

This is a Dueber Watch Company pocketwatch, 18 size, 17 jewels, model 4, "Grand", made about 1904.

To begin we have a discolored acrylic crystal and some rust damage on the hands.

Early types of plastics used for what they called “unbreakable” watch crystals tint with age. Yellow is the most common color but you’ll also see blue and green tones. The problem with this is that the plastic degases corrosion fumes while this is happening. Hands are almost always damaged and sometimes destroyed. The damage can spread too, to the cannon pinion, center wheel and other steel parts just inside the center.

Old plastic crystals that have changed color like this are probably long done releasing corrosive gases, but I don’t know. They should probably be replaced with glass, or modern plexiglass crystals which do not have this problem.

This movement has a really elegant tangential pallet (the older, English style escapement design).

For some reason this little flat spring seems to often be broken. It’s shown here loose, a replacement installed nearby. This spring doesn’t do much. It compresses when the lever is in just to give a little tactile feedback, and slightly hold the lever in.

Unfortunately I was not able to save the minute hand. This is a different one that I was able to fit. As usual when making the hole in the boss larger I over-shot and had to make it a little smaller again. I always seem to do that…

Project link (all the posts):
https://pluspora.com/tags/200006_et

Follow all the projects in detail here:
https://pluspora.com/tags/elgintime

And the album for this project is here:
https://photos.app.goo.gl/uD3uxSFQ4irjJigQ9

Job Number 190043

We see a lot of pocketwatches with discolored plastic crystals. They can appear tinted blue or green but yellow is the most common. Sometimes it appears that the color is the dial, but it's not.

The crystals are not supposed to be this way, they were originally clear. Over decades these early types of plastic decayed and changed. While doing so, they gave off a corrosive gas that very commonly, as is the case on this Hamilton, severely damages the hands and often the dial too. In the worst case, the corrosion will extend to internal parts inside the movement through the center of the dial.

It's temping to think that plastic crystals are always "cheap" replacements. But this is not necessarily so. Plastic crystals were considered a technological improvement over glass as they were said to be "unbreakable".

Some people prefer to leave these crystals on as original. This may be fine. Many believe that the degassing stopped long ago. On the other hand, some say that the old plastic crystals should always be replaced to avoid the risk of further damage. I don't know. This plastic crystal was replaced with glass.

Broken mainspring...

 The train...

The Hamilton pallet fork and pallet bridge...

Hamilton hairspring stud clamps, which are pretty small, have two small screws, one for each side of the stud. It always takes a little holding of breath to get these placed with the balance bouncing around, but there are a few tricks that make it easier.

Follow all my watch repair projects in detail here.

And the album for this Hamilton project is here.

New Arrival, Job Number 190166

This is another instance where an old-style plastic crystal has decade, yellowed and given off corrosive gases that have dissolved the hands. Often in such cases there will be other damage to steel parts under the dial. We'll see.

This is also a great example of a completely practical watch selection by the original buyer. It is in a low cost, plain nickel case, but it is a high-end Elgin Veritas movement, railroad grade. Also the case is a swing-out style which was required by some railroad specs. Even the plastic crystal is a practical choice. These were considered a technical improvement over glass and referred to at the time as "unbreakable" crystals.

My Grandfather once told me that the Veritas movement, one of Elgin's most expensive, cost about $85 at a time when he was making, as a skilled watchmaker, $24 a week.

New Arrival, Job Number 190106

At one time plastic watch crystals were considered an upgrade over glass as they were "unbreakable". Most people assume they are not original, but in fact they often are. Plastic used for watch crystals goes back much further than one might think. There were quite early formulations of acetate and acrylic materials common as early as the 19-teens. The problem with these early materials is that they decay over time becoming yellow, blue or green. And while doing that, a corrosive gas is released.

I see many watches like this one that internally, to look in the back, look great. Nothing is broken and there's no sign of rust, damage or excessive wear. But the hands are gone. The rust is too sever to save them, due to the crystal. Unfortunately, I often find in these cases that the cannon pinion and other parts near the center front of the movement are likely also damaged.

There are mixed opinions as to whether a discolored crystal should be left on the watch as original, or replaced with glass. There are mixed opinions as to whether to degassing continues decades after the discoloration has occurred (any chemists out there?). But most people want a glass crystal put on. Glass crystals are extinct in some sizes and types now, but usually there is a plexiglass substitute which is stable and almost indistinguishable from glass.

New Arrival

Many say that these early plastic crystals de-gas as they decay and corrode hands and dial, and even inside the watch. This is true, I have seen it.

This watch appears fine though. It is also said that once the crystal has turned green/yellow, it is no longer de-gasing, after all those decades. I don't know. But glass crystals do show off the dial more and are getting harder to find.

I advice people to replace the plastic ones, while you can.

New Arrival

An am occasionally asked about colored dials on antique pocketwatches. The dials in question are really white. Older types of plastic used for watch crystals tints yellow or green with age. This isn't an intentional design. Plastic crystal were available earlier than we might think, and the old ones change in this way. Interestingly, plastic crystals were actually more desirable for some watch customers at the time, than glass. "Unbreakable" watch crystals were considered modern and technological advance.

Sizing Pocketwatch Crystals

The labels on antique crystals used for pocket watches are fantastically cryptic. Let's take a look at a couple of examples.

This one, a rather large crystal, has three numbers; 20 10/16s, 24 and 3.

The most useful number is the first one. This number appears on Geneva labels. It is the crystal's largest diameter in lignes. Lignes are an obscure system of measure still commonly used to describe the size of watch movements.

In the 18th and 19th centuries, American watch companies used a different system referred to as the Lancashire Gauge, while European companies used lignes.

One lignes is one twelfth of an inch. That inch however is not the familiar English inch, but a Paris inch. A Paris inch is larger at 1.06577 English inches. A lignes therefore works out to 2.25583 millimeters.

• One lignes = 2.25583 mm
• 1/16th lignes = 0.141 mm

A 20 10/16s lignes crystal is 46.5266 mm in diameter.

Watch crystal lignes sizes are always, as far as I know, give in increments of sixteenths. Why 1/16s? A Paris inch is divided into 12 parts called lignes, as we noted. But that system further divides lignes into 12 parts called douziemes. A douziemes is thus 1/144th of a Paris inch. This increment is not precise enough for watch crystals. It was found that a sixteenth of a lignes worked out much better than using twelfths, and so that's the way it went.

Back to the label at hand, the lower number, 3, refers to the height of the crystal. This is an integer value that may range from 2 or 3 up to 8 or 9. The lower the number, the higher the crystal. Although a standard, the scale seems arbitrary and its origins are, to me, unknown.

Here is a second label.

This one just has two numbers. The first number has the sixteenths part, so that is the diameter in lignes.

The middle number on the label above, 24, and the second number on this label, 21 7/8 are a partial mystery.

The first number, 24, is in units of an even more obscure system of measure. These are lunettes. As a system of measure, these units appear to be unique to watch crystals. I know nothing about the origin of these units.

On this label, 21 7/8, does not make sense as 20 15/16 would be almost 25 lunnettes.

On many other crystal labels with three numbers, that third number will be the diameter in millimeters, usually tenths on millimeters, this 473 would be 47.3 mm. I didn't happen to have a crystal like that handy.

Glass Chip, How Did That Happen?

I found a tiny chip of glass sitting on the dial on this watch.  It appears to have come off the inside of the edge of the crystal.  Strange...  It's barely visible.  There's no sign at all of any injury to the watch or case.

This is an Elgin grade 82, 13 jewel version, made about 1885.  It;s a G. M. Wheeler movement.

GS Crystals

The following link it for a GS crystal catalog in PDF form. Enjoy...

https://drive.google.com/file/d/0B-qOxVSisTnKeEJhSGUwUkplTHc/view?usp=sharing