We report on the performance of a Magnetically Shielded Room (MSR) intended for next level 3He/129Xe co-magnetometer experiments that require improved magnetic conditions. The MSR consists of three layers of Mu-metal with a thickness of 3 mm each and one additional highly conductive copper-coated aluminum layer with a thickness of 8 mm. It has a cubical shape with a walk-in interior volume with an edge length of 2560 mm. An optimized degaussing (magnetic equilibration) procedure using …