  We report extensive spectroscopic and differential V-band photometric
observations of the 18.4-day detached double-lined eclipsing binary LV Her
(F9V), which has the highest eccentricity (e = 0.613) among the systems with
well-measured properties. We determine the absolute masses and radii of the
components to be M1 = 1.193 +/- 0.010 M(Sun), M2 = 1.1698 +/- 0.0081 M(Sun), R1
= 1.358 +/- 0.012 R(Sun), and R2 = 1.313 +/- 0.011 R(Sun), with fractional
errors of 0.9% or better. The effective temperatures are 6060 +/- 150 K and
6030 +/- 150 K, respectively, and the overall metallicity is estimated to be
[m/H] = +0.08 +/- 0.21. A comparison with current stellar evolution models for
this composition indicates an excellent fit for an age between 3.8 and 4.2 Gyr,
with both stars being near the middle of their main-sequence lifetimes. Full
integration of the equations for tidal evolution is consistent with the high
eccentricity, and suggests the stars' spin axes are aligned with the orbital
axis, and that their rotations should be pseudo-synchronized. The latter
prediction is not quite in agreement with the measured projected rotational
velocities.
