I was given a couple boxes of old traps mostly dls and a few coil springs
on most of the DLS there is a small pointed piece of metal near the end of the chain -
what is it and what is its purpose ?

Pin the trap to a tree or post

Was used as an anchor, drive it in like a nail. They hold great!

thanks guys

Not only did they include the "nail anchor", but the ring they are on was made with heavy wire closed by a wrapped splice. No way that was coming apart. Modern era way to duplicate the nail anchor is to use a fence staple. A long one.

Many modern era traps still include the ring, but these days are simply spot welded. For those, I tend to either cut off the ring or simply bypass it with a swivel tied directly to the chain. Has anyone had these spot welds fail?

Only thing I use those modern era rings for is marten, I don't trust them for anything else. So no I haven't had them fail, but that is because I only use them on 120s for marten.

It is called a spad !!!