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With NuSTAR comma it is possible for the first time to determine the compact object type and accretion state of large samples of X-ray binaries openParXRBsclosePar in nearby galaxies. This classification comma based on hard X-ray luminosity and hardness ratios comma can provide valuable insights into how XRB properties vary with variables such as metallicity openParZclosePar comma age comma and specific star formation rate openParsSFRclosePar. Vulic et al. openPar2018closePar classified 90 XRBs in nearby galaxies observed by NuSTAR comma but the sample contains few galaxies with low-Z or low sSFR. Furthermore comma variability studies of XRB populations have been limited to M31. We propose joint NuSTAR-XMM observations of the NGC 55 to expand studies of the compact objects comma accretion states comma and variability of XRBs to lower luminosities in a low-Z galaxy.