How it's made?

[challenger]

No spring or "serviceable" parts. Simply a male and female mating with surprisingly little tolerance. If you live near a surf location go find one please. I think you will be as interested as I am.

[Doozer]

No user serviceable parts inside.

That statement assumes the level of intelligence of the user.
Bad met to make.

-D

[LKeithR]

Perhaps internal and external grooves and a square section spring ring that is just flush in the male part when the parts are pushed together. Then as the grooves line up, the spring snaps into the outer groove which is only half the depth of the ring section.

The ones I've seen are made that way. A good stiff spring ring that is compressed for assembly and springs
in to place when the parts align. As has been pointed out; there's no way to service it once assembled...

[Mcostello]

No user serviceable parts inside.

[old mart]

Perhaps internal and external grooves and a square section spring ring that is just flush in the male part when the parts are pushed together. Then as the grooves line up, the spring snaps into the outer groove which is only half the depth of the ring section.

[wierdscience]

On at least one type, male stub on one half, female socket on the other, both with an annular half round groove. Male goes into female, stainless steel balls are loaded into the annular groove through a hole in the side of the female. Hole is filled with a tapered plug and peened over.

[754]

Bronze I bet.. I would like to know too, may be use full for future work..

[OaklandGB]

Maybe a ball end shaft pressed into a slightly oversized socket, then rolled under pressure to close it around the ball? But looks like it was also turned?
I guess you could put it on a band saw and slice it down the center to see the internal structure, but it looks great as a useful swivel.

[challenger]

I'll start by asking how this swivel is made? It goes on a surf board leash. Seems like brass but has more of a copper color. The two pieces fit perfectly together and swivel with precision.
I can't image how this was accomplished?