As stamcon wrote, there was no spring inside. Just a lot of soil!
What I found fascinating is that it was able to clean up into such nice condition--even though it's just a wire connector
As to the crimp connectors, I recall reading in one of Rex Cauldwell's books that the proper way to crimp is with a device that will apply equal pressure from all sides.
I have noticed that the orange store carries caps to cover the crimps on current-carrying conductors.
Are those crimp-on barrels also properly used for splicing together the bare ground wire in NM cable?
The DIY book I bought at the orange store shows that use. However they just show the brass "sleeve" crimped over a bundle of bare copper wires - no rubber sleeve or anything.
I came across & still have (somewhere) some of those same Simplex - Holland wirenuts... I have a regular customer in Ocean Beach (San Diego) who owns a house built in 1927.. Those were used at pretty much most of the existing light fixture locations, along with the funky wax-coated cloth wire.