Why does my chain have a single hollow pin? I have some version of a SunRace 10-speed chain, and I'm curious as to why it seems as though each pin is a regular "non-hollow" pin, and a single one on the chain is hollow.  Is this some kind of a master link?  I couldn't tell via - How can I tell if a chain has a master link?.
Its not a master link - that's probably the one-use pin that was used to close the chain the first time.

This is what a Shimano pin looks like after its been snapped off.   There's a clear difference to show this pin should not be pushed out again because the plate holes will be enlarged slightly.



Your one doesn't look quite the same - it does look like a snapped off line exists though.  This was probably a hollow connection pin rather than the solid one supplied with that chain, or perhaps sunrace pins are all hollow.