This is an exact clone of the Boss LMB-3 circuit, with a nearly identical metal casing.
Controls cover output level, threshold, ratio, and an enhancer, which is a variable 'smile curve'. As with the Boss, despite it's name this will do everything from hard limiting to the subtlest levelling compression. It shows the lightest signs of use, and comes boxed with instructions. I still have one on my pedalboard, just clearing out my spares!
£15 posted