Could they be for holding a chain still mounted on a bike under tension while adding or removing a link to a section which would be held in the open center of the tool? I assume the "hooks" at the bottom of the open space could prevent the chain from slipping off of the tool.
VAR made an effective chain holder tool [VAR #424 "Monte-chaines"] for similar purpose. Handy when installing a separate link... you don't need to wrestle with chain tension to make the chain slack while attaching a new outer plate.
BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA