Bit of a curio this fella, and very much of the homemade variety. The normal way to join wire slings together is by using a swage which is best described as a pressure weld. In this case the maker has simply spliced the wire and used more copper wire to secure the ends. The little wedge on the end is also homemade; simply cut and filed from a piece of aluminium. Two elderly climbers gave this, and one or two other items of gear, to our Mountain Guide friend, Dave (Smiler) Cuthbertson, in 2014 and he kindly passed them on to us. Unfortunately, we don’t know who the two gents are so we can’t get any more info – a pity.