The ternary stannide CeRuSn is a static mixed-valent cerium compound with an ordering of trivalent and intermediate-valent cerium on two distinct crystallographic sites. ¹¹⁹Sn M¨ossbauer spectra showed two electronically almost identical tin atoms at 323 K, while at 298 K and below (77 and 4:2 K) two tin sites can clearly be distinguished. Solid-state ¹¹⁹Sn NMR experiments were performed to probe the local hyperfine fields at the two different Sn sites. Powder ¹¹⁹Sn NMR spectra are nicely fitted with two Sn sites with nearly the same magnetic anisotropy, but with different absolute shift values. Both Sn sites are strongly affected by crossover-like transitions between 100 and 280 K. This local-site study confirms the superstructure modulations found in previous investigations. Towards lower temperatures the powder NMR spectra are broadened giving strong precursor evidence for the antiferromagnetically ordered ground state.