One of the things I want to do is to use the PWM of the AVR to put a high frequency onto the coils. Not unlike the way one puts similar signals onto the Ethernet magnetics. Or Pipe organ relay magnets. (which are also telephone switched networks.) The idea is to look for EMF reflections. All coils will have an impedance which is measured in ohms. It is a fundamental of the length of the wire which causes a voltage drop in a straight wire. When coiled the back EMF affects this.
I see the data sheet list the coil resistance as 2 to 3 K ohms. Cheap digital meters often have fairly high current voltage. Usually the data sheet will give the impedance of the meter. Pipe organ magnets have resistances in the 10s of ohms and use voltages in the 12 to 25 range.
The coil can also work like an antenna. So putting a frequency into one end and looking at the EMF can also be used to detect a broken coil. (or a bad network cable)
There are plenty of watch timer testers out there what read this. I am sort of a do it yourself sort of gal, so am looking more at the challenge, or what to do wit a tray of left over AVR processors.
Most of the time a coil breaks is near the contact terminals. Often the first few windings can be teased out. If there is an over current the wire will act like a fuse. This will melt through the weakest part which will be closest to one of the terminal as the electrons are acting like cars on a freeway all trying to merge past the narrow point. Sand in an hour glass does the same thing.
I only have a cursory understanding about magnetics. Magnetic fields do have to have a completion pole. Ironically I was part of some patent discussions where this was discussed in front of me. This material is often pure sintered iron or nickel. Funny things go one with magnetics. There is something called spin. A friend of mine worked for IBM ins the spintronics dept. Rule no one is there are no quantum mechanics in industrial applications. IBM wound up calling the product 'Fairy dust." The curious thing is when electron spin is converted to light, the light is polarized. Such is what makes your hard drive work.
See the data sheet refers to parts 1, 2 , 3 and 4 as a magnetic circuit. I think this is the same as the frame of a pipe organ magnet. Some of this is shaped and sintered into permanent magnets to complete these fields. And Maxwell's equations are hard to follow. Somewhere I have some green film what shows magnetic flux lines. When I get my watch I may try it and see if there is enough magnetism to leave a shadow.
I suspect looking over the data sheets some of this is a bit obfuscated. While at the same time clearly drawn with a CAD application.
The short of it this is what is called a BLDC motor. (Brush Less Direct Current) Which are really AC motors. There is quite a bit of theory written on these as most computer fans are such beasts. Modern automotive also uses them.
I also bought some swatches to break up and see how they function. I noticed that the newer movements use mechanical setting. The magnetic clutch is novel to me and I still have not set my Tissot from the recent time change.