They were included when you purchased a radio (and sometimes even if you DIDN'T purchase a radio!!)
The original concept of these was to dissipate static. As the car's wheels rotated, static charges would build up because the hub and wheel bearings were insulated from each other by grease. Iintermittant contact between the hub and the wheel bearings would cause the static to be discharged. This in turn would produce interference (snap, crackle, pop!) on the car's radio. The static collector "springs" were placed inside the two front dust caps to create a constant electrical path between the axle and the bearing, thus eliminating the static discharges. GM finally figured out that they really weren't necessary and discontinued them in the late 60's. As a matter of fact, they're not even shown in the 69 AIM. The 68 AIM is the last time they're shown, so I believe 69's didn't come with them. John can verify that.
Here's what they look like: