Not sure of the make (could be a surly) but it's a bolt on version, not sprung, so it's very rigid. It fits over the axle and is secured by both the wheel nut and a seperate bolt so you can get the tension nice and tight.
As it's only taking up about half a links worth of slack, the chainline isn't too far out. I think it only pulls the chain away from 1 tooth at the most on the rear cog.
where does the other bolt go?