High-precision mass measurements of stable and beta-decaying nuclides [52][53][54][55][56][57] 55 Mn, 56,59 Fe, 59 Co, 75,[77][78][79] Ga, and the lanthanide nuclides 140 Ce, 140 Nd, 160 Yb, 168 Lu, 178 Yb have been performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The new data are entered into the Atomic Mass Evaluation and improve the accuracy of masses along the valley of stability, strengthening the so-called backbone. The mass of neutron-deficient 168 Lu in its isomeric state has been measured directly. The mass of neutron-rich 178 Yb indicates a change of nuclear structure approaching the double harmonicoscillator shell closure for Z = 70 and N = 112.Open Access This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.