Tip- Removing the back of these old pocket watches is sometimes difficult if the threads are dirty, or the back put on too tightly, or cross-threaded. Some of the Fortune, Wadsworth and other cases have no knurl or ornament around the edge of the front and back parts, and are hard to open.
A pair of Atlas therma gloves works wonders, they stick to those smooth surfaces like glue. (Also good for food jars, etc.)

When you get a new (old) watch, clean the threads and contact surfaces with a bit of soft cloth.