[en] The ¹S₀-³P₀ clock transition frequency ν_Sr in neutral ⁸⁷Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the 1x10^-15 level makes ν_Sr the best agreed-upon optical atomic frequency. We combine periodic variations in the ⁸⁷Sr clock frequency with ¹⁹⁹Hg⁺ and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant α, electron-proton mass ratio μ, and light quark mass. Furthermore, after ¹⁹⁹Hg⁺, ¹⁷¹Yb⁺, and H, we add ⁸⁷Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of α and μ