It is used to quickly assemble, dismantle, and reassemble lifting chain slings and rigging chains.
The Working Load Limit (WLL) is 5.4 tons, as indicated by the "WLL 5.4T" text on the link.
It is made from drop-forged alloy steel and is coated in red paint.
The markings "13-8" and "18-8" likely refer to the size and grade of the chain or components it is designed to connect.