A novel implantation-decay technique has been employed to measure the magnetic moments of the 2 1 1 states in the neutron-deficient nuclei 184 Pt, 186 Pt, and 188 Pt. The magnetic moment systematics for the even Pt isotopes now extend from 184 78 Pt 106 to 198 78 Pt 120 , spanning the upper half of the valence neutron shell. Despite the prolate-to-oblate shape transition near A 190, they remain remarkably constant. The g͑2 1 1 ͒ values for 184,186,188 Pt are consistent with shape-coexistence models in which the deformed configuration has a larger effective number of valence protons than the less-deformed configuration.