100% Bronze Jump Rings. Bronze is an alloy of copper and tin.
Slightly lighter in colour to copper (not as rosy) it will tarnish over time and turn a colour like you see in bronze statues. It can be cleaned with any commercial brass cleaner or by placing it into a vinegar/water mixture for approx 30 second and rinsed under clean running water.
The temper of the wire is half hard (HH). Alloy is C510 also known as phosphor bronze.