Restoration of a miniature Patek Philippe pocket watch

Antique Miniature Patek Philippe	Restoring a very small Patek Philippe pendant watch was an interesting project. It had some missing parts as I received it. The bezel and crystal of the small hunter case and also the cylinder of the movement were missing. The balance wheel had been very nicely glued into position. Otherwise the watch was in good condition.
	Making the bezel and fitting the crystal were fairly strait forward and familiar tasks but making and fitting the tiny cylinder was more challenging. The following is a chronicle of the process of making the cylinder. Some technical observations have been added. I hope you will find the information informative and entertaining. The cylinder escapement is not rare. Invented by Thomas Tompion in the later 17^th century, it was the first improvement over the verge escapement. Millions of cylinder watches have been produced. Although it is considered inferior to the more “detached” lever escapement, it is capable of respectable performance in practical use. Unfortunately many modern watchmakers do not respect them. One thing is for certain. Craftsmen should be familiar with its function before attempting to provide service for them.
Some watches were constructed using a piece of ruby or sapphire as the cylinder section of the balance staff (see right). More commonly the cylinder is a small hollow tube of steel that forms the very center of the balance assembly of a cylinder escapement watch. A portion of the tube is cut away allowing the teeth of the escape wheel to pass through. As these teeth go by the lips of the cylinder they push the cylinder, first one way then the other, causing the balance to swing like the pendulum of a clock. It is a dead-beat escapement with no recoil.
	A very interesting watch indeed, it has an 18 Kt. yellow gold case and, as you can see, it is signed with the serial number. This number according to my records would indicate a production date around 1880.
Not signed by the maker, the movement bears the same serial number on the dial side. Finish is high quality and the mainspring and barrel in this watch are very unusual. The movement has a slipping mainspring of the type that is commonly found in modern self-winding watches. As the watch becomes fully wound the pressure of the inner coils of the mainspring is removed from the outer coil and the tail is allowed to slip from notch to notch. Also, this is a single piece mainspring that tapers to twice as thick on the outside coil. There is no bridle.
The watch winds and sets with the crown and cannot be over-wound because of the slipping mainspring arrangement. There is no need for a stop-work mechanism with the slipping mainspring. Watches without recoil click arrangements can be over-wound. Over winding is not a fable. It is also true that cylinder watches can stop running if too much power is applied to the train. They will stop on the lock because the balance spring cannot overcome the friction of the escape teeth against the cylinder wall when the force is too great. A tiny watch is especially susceptible to stopping on the lock because the balance spring is so light.	I do not know who invented the slipping mainspring. Mr. Manuel Yazijian CMW (AWCI Instructor) has observed that Georges Frederic Roskopf used the feature in the late 1860's. I suspect it was invented when a barrel hook failed. It could not have been considered useful until the fusee was discarded. That would not happen until after the cylinder escapement demonstrated some tolerance to variations in driving force.
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