I had a problem with a solenoid on a 66 289 I bought in 1988. When I took it apart (I drilled the rivets), I found the jumper strap from the internal copper disc to the terminal for the 12V to the coil was broke. It was braided copper, I assume for flexibility. The one shown in Scotts pictures has what appears to be a thin solid copper strap, a later version. The symptoms for the problem were the engine would crank, but would not start - no 12V direct to the coil from the solenoid. When you released the key from ignition, and the ignition switch dropped to run, there was enough voltage to the coil (9V), and enough spin left on the engine to get the car started. That was one of many "little" problems I had to attend with over the years. (Still got the car.)
Jim