  We studied one of the most X-ray luminous cluster of galaxies in the REFLEX
survey, RXC J1504.1-0248 (hereafter R1504; z=0.2153), using XMM-Newton X-ray
imaging spectroscopy, VLT/VIMOS optical spectroscopy, and WFI optical imaging.
The mass distributions were determined using both the so-called hydrostatic
method with X-ray imaging spectroscopy and the dynamical method with optical
spectroscopy, respectively, which yield M^{H.E.}_{500}=(5.81+/-0.49)*1.e14Msun
and M^{caustic}_{500}=(4.17+/-0.42)*1e14Msun. According to recent calibrations,
the richness derived mass estimates closely agree with the hydrostatic and
dynamical mass estimates. The line-of-sight velocities of spectroscopic members
reveal a group of galaxies with high-velocities (>1000 km/s) at a projected
distance of about r^{H.E.}_{500}=(1.18+/-0.03) Mpc south-east of the cluster
centroid, which is also indicated in the X-ray two-dimensional (2-D)
temperature, density, entropy, and pressure maps. The dynamical mass estimate
is 80% of the hydrostatic mass estimate at r^{H.E.}_{500}. It can be partially
explained by the ~20% scatter in the 2-D pressure map that can be propagated
into the hydrostatic mass estimate. The uncertainty in the dynamical mass
estimate caused by the substructure of the high velocity group is ~14%. The
dynamical mass estimate using blue members is 1.23 times that using red
members. The global properties of R1504 obey the observed scaling relations of
nearby clusters, although its stellar-mass fraction is rather low.
