Was going through some of my deceased dad's tools, and found this odd thing, looks like some sort of a hand-held mini pressing tool, or a mini bearing puller. If it helps my dad's line of work was machinist.
Yes. Chain breaker. Grind the head off of the chain link "pin" then push the pin through to the other side with this tool. Chain comes apart. There's usually different size pins to mate up to the chain. But that tool is large enough to do at least a 520 series motorcycle chain.
If one looks closely at the tool you will see the link size on the plates used for holding the tool together. That particular tool is for 60 sized chain.