Name that Ware, January 2024

The Ware for January 2024 is shown below.

I picked up this little gizmo at a junk shop in Akihabara. I actually have no idea what the original purpose was, so I’m curious to see if anyone can convince me as to what this thing did, presumably for many years and millions of times. I got it mostly because it was a great price for a linear guide plus associated optical interrupters and motors (although I think the central motor’s bearing is busted, hence its junk shop fate). Fortunately the mounting patterns for these kinds of mechanical parts are almost, but not quite, standardized.