In a high-energy fragmentation experiment at GSI an I-pi = (6(+)) isomer and its gamma-decay are identified in Sn-102, the two-neutron neighbour of the doubly-magic Sn-100. Its half-life is measured to be T-1/2 = 367(11) ns. The possible existence of further isomers is discussed in the framework of large-scale shell model (LSSM) calculations including up to five particle-hole excitations of the Sn-100 core. From the precise B(E2; 6(+) -> 4(+)) strength and the recently remeasured value for B(E2; 8(+) -> 6(+)) in the two-proton hole neighbour Cd-98 effective E2 polarization charges for protons and neutrons were inferred including LSSM corrections within the full N=4 0h omega space. The results are discussed in comparison to predicted and empirically determined effective operators.