What's this hole pattern?

Anybody know what this hole pattern is? What's up with the one hole at the top (near the silver sticker)? Thanks in advance.

its a marker that was mounted with a piston system, some of those have a little flimsy arm (that is mounted with screw about six inches ahead of the binding) that does nothing, but they claim it engages the piston sooner

Ah, thanks. That would explain why I couldn't recognize it.