You are looking at a vintage Marx lock on. This is the style that sticks into the bottom of the track for a snug fit. It is really the best way to connect to 027 track since they slide in and stay rather than clip. Also used with some accessories.
THIS IS THE VERSION OF THE CLIP WITH THE MORE TRADITIONAL FAHRENSTOCK CLIPS. Many Marx lock ons have the fatter style of wire clip where you push down and thread it. This one has the more common clip that you thread the wire through. You can find the fatter style in our other listings.
This one is clean and ready to use. Shows light signs of use and a little bit of oxidation. We have more than one available, so the picture is not the exact item, but it will be in similar condition.
Many folks use these for other brands of toy trains as well such as Lionel, K-Line, even American Flyer.