We often find various wiring harness jumpers or extenders, ones with plugs on both ends with a short section of wiring to connect two different harnesses or electrical component. The above one is for connecting the early 1967 C-4 neutral safety switch to the upgraded wiring harness with the 4 gang plug. It wasn't always used, have seen the individual male / female plugs, plugged directly into the 4 gang plug too.
Midlife, you've probably seen a few in your time too?