The copper section on top of the armature is called a commutator, and is divided into 3 sections for our motors. There are 3 windings on the armature, and one end of each winding gets soldered to its' corresponding commutator section. If you notice one wire not soldered to a commutator section, it must be repaired, or the motor will not run. Most likely the wire gets soldered to the tab on the commutator section visible in the photo.

Larry