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This Seth Thomas Adamantine mantel clock is dated June 1918 on the bottom of the case (date code 81F, where F represents the month, and 81 are the last two digits of the year reversed). I’ve seen many examples on earlier clocks where the date code has all 4 digits of the year, but this is the first time I’ve seen just 2 digits.

This later example of the Adamantine case has a simplified design with no pillars or Lion’s heads, and the dial is painted metal. See Seth Thomas Adele Adamantine Mantel Clock for an example of the earlier case design.

Case height 10 inches, width 12.5 inches, minute hand length 2 9/32 inches. The pendulum bob is lead with a brass cover on one side, weighs 5.4 ounces and is 45 mm in diameter.

The original mainsprings have the following measurements:

Time: 3/4 inch wide by 0.0175 inch thick

Strike: 3/4 inch wide by 0.0171 inch thick.

See more photos.

Job 5577. I did limited repair on the movement: cleaning, polished the worst pivots, installed 8 bushings (correcting 3 that were previously installed off-center), and tightened the strike click rivet.

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3. Seth Thomas “Adele” Adamantine Mantel Clock
4. Seth Thomas Red & Black Adamantine Mantel Clock
5. Seth Thomas Green and Black Adamantine Mantel Clock, Rear Escapement

The model name of this Adamantine mantel clock is “Adele”. When it was new the case was deep red, but it has faded to red-orange. The clock is 11 1/2 inches tall and 12 1/2 inches wide at the feet. The minute hand is 2 1/8 inches long.

The movement is labeled “4 1/2″ on the back, but it is the same as the No. 89 movement. The name “Adele” is stamped in ink on the bottom of the case. There may be a date code as well, but it is very faint.

See more photos.

Repair job 5564. This clock has its  original mainsprings marked Seth Thomas. They are both 3/4 inches wide and 0.0175 inch thick.

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5. Seth Thomas “Adamantine” Mantel Clock with “Ding Dong” Strike

This beautiful Seth Thomas green and black Adamantine mantel clock has the older type of movement with rear escapement. See my clockhistory.com web site for some history of Seth Thomas Adamantine clocks. This clock is 11 3/8 inches wide and 12 1/2 inches tall. The dial is not original, and has a 4 1/4 inch minute track.

The time click was broken in two when this clock came in for repair. The strike click was a previous replacement that was located incorrectly. I installed two new clicks, and the original wire clicksprings were in good condition. I also polished the pivots, installed 12 bushings, and replaced the wires in the escape wheel pinion.

The mainsprings appeared original, the time spring measuring 11/16 x 0.0175 inch, and the strike spring measuring 11/16 by 0.0183 inch. They were in good condition and so were retained in the clock. If they needed replacing, I would have used thinner ones, 0.0165 inch thick.

See more photos.

Repair job 5437.

Related posts:

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2. Seth Thomas Mahogany Adamantine Mantel Clock
3. Seth Thomas Mahogany Adamantine Mantel Clock
4. Seth Thomas “Adamantine” Mantel Clock with “Ding Dong” Strike
5. Seth Thomas Adamantine

This Seth Thomas Adamantine mantel clock is dated April 1902 on the bottom. The case is 17 3/4 inches wide (at the feet), 10 3/4 inches tall, and the paper dial has a 4 1/8 inch minute track.

The date code stamping of 2091 D on the bottom means April 1902.

The movement is marked 4 1/2 on the back, and it is the same as the movement later called No. 89 or 89C.

The movement took extra time to clean, as the oil oil was very hard and dry. I polished the pivots and installed 14 bushings, reversed the pinion wires in T5, and tightened the click rivets.

The original mainsprings were 3/4 wide and 0.019 inch thick. The time mainwheel had significant wear (for some reason the strike mainwheel teeth had little wear). I replaced the mainsprings with thinner ones to reduce future tooth wear. I used Timesavers part number 15959 3/4 by 0.0165 by 120 inch mainsprings. The new time spring measured 0.0165 inch thick, while the new strike spring measured 0.0168 inch thick. These long thin springs, besides reducing wear, help achieve uniform timekeeping over a 7 day run.

The glass in the bezel is a 5 1/2 diameter inch flat glass.

See more photos.

Repair job 5365.

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2. Seth Thomas Mahogany Adamantine clock, 4830
3. Seth Thomas Red & Black Adamantine Mantel Clock
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5. Seth Thomas “Adamantine” Mantel Clock with “Ding Dong” Strike

This Seth Thomas Adamantine mantel clock is dated March 1901 on the case bottom (date code 1091C). The case is 12 1/8 inches tall, 17 5/8 inches wide at the feet, and the minute hand is 2 1/8 inches long from center to tip.

See more photos.

Adamantine is Seth Thomas’ patented process of applying colored celluloid to wood clock cases.

The movement has a recoil escapement located at the rear. (This is the first type of movement used in Adamantine clocks, and was phased out and replaced with the No. 89 movement around 1900 – 1901. March 1901 is the latest use of the rear-escapement movement that I have seen).

This clock has a metal dial with cutouts though which the numerals on a paper dial can be seen. The regulator is above the numeral “12″. (Clocks with No. 89 movement have the regulator below the center of the dial.)

This movement uses loop-end mainsprings that are 11/16 inches wide. This clock has the original mainsprings. The time spring is 0.018 inches thick, and the strike spring is 0.019 inches thick. If the springs needed  replacing, I would use 0.0165 inch thick springs. The original springs in this this clock were fine, so I cleaned and reinstalled them.

Here is a video of the escapement, and the clock striking:

Repair job 5369.

Related posts:

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4. Seth Thomas “Adamantine” Mantel Clock with “Ding Dong” Strike
5. Seth Thomas Adamantine Clock

Here is a Seth Thomas “Adamantine” clock with black and green marbleized finish (Adamantine is Seth Thomas’ patented celluloid finish that was made in many colors to imitate wood and marble). It strikes the hours on two brass bells, and strikes the half hour on the higher pitched bell. The clock was sold on March 22, 1916 (22 March 1916 is written on the label on the back cover). My customer’s grandparents received this clock as a wedding gift from family members in June 1916.

The case is 18 1/8 inches wide at feet, 11 1/16 inches tall, with 4 1/4 inch time track on dial.

Below is a slideshow of more photos:

Here is a video of the clock striking:

Here is a movie of the escapement action, first run down 7 days, then fully wound:

Repair job 5094. No. 89T 8-day time and bim-bam strike movement.The time mainspring is a 3/4 x 0.0172 x 96 inch mainspring from R & M Imports (opened to 8 inches when unclamped. The time spring was original, but I replaced it because it had a squeaky and jerky action which sometimes indicates it will break soon. This movement needs a slightly stronger time mainspring than the regular No. 89, as the half-hour strike hammer is lifted through a great distance. The strike mainspring is the original (marked ST) 3/4 x 0.0165 inch spring. It opened out to only 6 inches in diameter when uncoiled, yet provides plenty of power to operate the striking for over 8 days.

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2. Seth Thomas Adamantine
3. Seth Thomas Mahogany Adamantine clock, 4830
4. Mainsprings for Seth Thomas Queen Anne, Time and Strike, with Second Hand
5. Seth Thomas Adamantine Clock Movement with Thin Time Mainspring

“Adamantine” was Seth Thomas’ trademarked name for a celluloid finish over wood. Besides the mahogany color shown here, it was made in black, white, green, brown, tan and other colors. These cases are durable, and can usually be polished to look very nice. Sometimes the colors fade with age. Adamantine clocks were made from about the 1880s to the 1920s.

This beautiful mahogany Adamantine clock came into my shop recently with a broken time mainspring. Nothing too exciting about that, but I think this clock is so nice looking that I decided to show it here. I had previously repaired it 11 years ago, overhauling the movement and polishing the case and bezel.

I replaced the broken time mainspring with a Merritt’s P-1956 3/4 by .0165 by 96 inches (the original spring was 0.0172 inch thick). The pendulum takes a superb motion (almost too good) and so an even thinner mainspring would work. During my previous overhaul, I replaced the way too strong strike mainspring (an incorrect replacement) with a spring about 0.016 inch thick.

Repair job 4981.

Related posts:

1. Seth Thomas Mahogany Adamantine clock, 4830
2. Seth Thomas Sparta Adamantine Mantel Clock
3. Mainsprings for Seth Thomas Adamantine, 89C Movement
4. Seth Thomas Adamantine Clock
5. Seth Thomas Adamantine

I just repaired this Seth Thomas mantel clock in a mahogany color Adamantine case. It has a No. 89 movement with a solid back plate. The case is 16 1/4 inches wide (including feet) and 11 inches tall. The bottom of the case has date code 81B (February 1918).

The escape wheel had two teeth that were too short due to damage by a previous repairer. The slide show below shows that the damaged teeth were removed, a brass plug inserted, and then 2 teeth filed to shape.

Both mainsprings were original Seth Thomas springs, one .0177 inch thick and the other .0165 inch thick. I don’t know for sure which one was originally on which side (time or strike). The .0177 inch thick spring was too strong. The thinner spring did not unwind smoothly. I replaced both with Merritt’s P-1956 springs 3/4 inch wide x 0.0165 inch thick x 96 inches long.

One thing strange about the case is that one end is mahogany Adamantine, but the other end is black! (see slide show below). It appears to have been made this way.

Repair job 4830

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4. Mainsprings for Seth Thomas Queen Anne, Time and Strike, with Second Hand
5. Seth Thomas Sparta Adamantine Mantel Clock