This AC adapter powers several older models of Dunlop pedals, which required a 3.5 mm, or 1/8”, plug as opposed to the 5.5mm x 2.1mm barrel plug required by current models.
The Long Story
Models which used this power supply include: EW95V, GCB81, GCB95 (old version), GCB95FW (old version), GCB95O, GCB100 (old version).