  We present time-resolved spectroscopic and polarimetric observations of the
AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster
Messier 67; new proper motion measurements indicate that EU Cnc is indeed a
member of the star cluster, this system therefore is useful to constrain the
formation and evolution of magnetic cataclysmic variables. The spectra exhibit
two-component emission features with independent radial velocity variations as
well as time-variable cyclotron emission indicating a magnetic field strength
of 41 MG. The period of the radial velocity and cyclotron hump variations are
consistent with the previously-known photometric period, and the spectroscopic
flux variations are consistent in amplitude with previous photometric amplitude
measurements. The secondary star is also detected in the spectrum. We also
present polarimetric imaging measurements of EU Cnc that show a clear detection
of polarization, and the degree of polarization drops below our detection
threshold at phases when the cyclotron emission features are fading or not
evident. The combined data are all consistent with the interpretation that EU
Cnc is a low-state polar in the cluster Messier 67. The mass function of the
system gives an estimate of the accretor mass of M_WD >= 0.68 M_sun with M_WD ~
0.83 M_sun for an average inclination. We are thus able to place a lower limit
on the progenitor mass of the accreting WD of >= 1.43 M_sun.
