Wow, a blast from the past. I have one in the garage that has not been used in 15-20 years. Tom you are right, colored contact points and a key or piece that you have to put on the collar or transmitter, I can't remember which one. I always hated those old collars. They are not very just for a judge. The stimulation level varies each time you press the button.
If you can give $15-20 for it you can trade it in and save a few bucks on a new collar, but I would not use it on one of my dogs
I had one years ago working with bird dogs. When working several dogs, it was a real pain trying to determine which points to use on the different dogs. You'd be better off to buy the new technology with the stimulation adjustments on the transmitter. You and your dog will both like it better.