We report the discovery of a less symmetric crystalline phase of Mn, acetate, a triclinic phase, resulting from recrystallizing the original tetragonal phase reported by Lis in acetonitrile and toluene. This new phase exhibits the same structure of Mn, acetate clusters and the same positions of tunneling resonances on the magnetic field as the conventional tetragonal phase. However, the width of the zero-field resonance is at least 1 order of magnitude smaller can be as low as 50 Oe-indicating very small inhomogeneous broadening due to dipolar and nuclear fields.