Restoration of a miniature Ivory watch

In an article published in the October 1999 issue of the “NAWCC Bulletin” Ted Crom describes a watch made substantially of ivory. This watch bearing the name “Simeon Holton, Ivory Watch, Middlebury” was submitted to me for restoration. Considering my propensity for a challenge, combined with a curiosity about the unusual, it was inevitable that I would be accommodating. As usual when undertaking anything previously untried, a few lessons were learned. The design of the watch is very typically Swiss. In fact, I believe parts of this watch were simply reproduced in ivory while retaining the steel pinions etc. of a more common watch. The barrel arbor has a square section on the lid end. This square indicates that the barrel arbor was prepared to receive a stop work finger. The ivory barrel lid has no such stop-work mechanism.	It is reasonable to think that, if the stop work had been duplicated, the ivory material of the lid would not have been tough enough to support it. For this reason, I believe, the stop work was abandoned yet the arbor retains its original square. At first it seemed the undertaking would be fairly routine. The barrel wall was broken out where the hook for the mainspring was installed. This hook had been left too long allowing the mainspring coils to concentrate pressure on it when unwound. I think that this hook had been the work of a previous repairman although I cannot be certain. The mainspring was oversize for the application and was obviously not original since it was of the modern alloy replacement type. There was also residual glue where the barrel lid had attached to the barrel. A new barrel would remedy all of these troubles when fitted with an appropriate size spring. When some pressure was applied to the center wheel, the balance began to oscillate, indicating an otherwise healthy watch. With a piece of ivory in hand, thoughtfully supplied by Dr. Crom, I set out to put the ivory watch back running. I had no experience with an ivory watch. While I have repaired a number of unusual watches, most of my experience has been with steel and brass etc. This watch is different in couple of ways.
	The obvious difference is that the main wheels and the time train wheels, except for the escape wheel, are made of ivory.
A not so obvious difference, important to the mechanic, who undertakes to get the watch going again, is the unusual and somewhat unknown history of the watch. All of the watches that I recall repairing in my experience were at some time relied upon to keep time. The repair history of those watches sometimes provided some unexpected situations but it could be safely assumed that, at one time, they were in working order. If necessity is the mother of invention certainly, assumption is the mother of error.
	Replacing the barrel required cutting the ivory as would be done with a brass replacement. The same technique using a fly cutter and index plate with a latch was employed.
The blank was left extra large in length so that, if the first attempt went amiss sometime after the teeth were cut, a second attempt would not require starting from scratch.
	The cutter used was produced from high-speed steel and carefully reproduced the tooth profile of the original part. The dimensions of the original ivory barrel were also copied.
After considering the failure of the original barrel, I thought it best to reinforce the replacement with a metal rim placed inside the ivory. Ivory seems to have a plastic quality. When placed under ample stress for extended periods of time it will deform. Many other materials will also do the same thing. The brass material originally intended for the design is much tougher however and would not have failed even when so abused.	I suspected that the ivory barrel wall might expand under the constant force of the mainspring. In fact, there was evidence of this happening to the original ivory barrel. The lid and barrel had residual glue remaining where the lid attached and the lid no longer seemed to fit snugly. Page 2