We re-analyze published proton beam dump data taken at the U70 accelerator at IHEP Serpukhov with the ν-calorimeter I experiment in 1989 to set mass-coupling limits for dark gauge forces. The corresponding data have been used for axion and light Higgs particle searches in Blxfc;mlein et al. (1991, 1992) [1] and [2] before. We determine new mass and coupling exclusion bounds for dark gauge bosons.