Where another component is added to the original single coil spring, it may be another spring with a shorter assembled height, smaller ID and OD, and thinner wire, with an extra step on the collar's lower surface to locate and pre-load it.
Another common alternative is a counter-wound damper, which is usually a thin, flat spring tightly fit inside the outer spring's coils. It suppresses harmonic vibration in the outer spring by friction as the springs pass each other in opposite directions as they compress.
The Corvette dual springs are:
Outer 3836123
Inner 3836132
Also shows a different collar, but only for the exhaust?
