  Three independent sets of stellar theoretical models are tested with
well-detached systems of the Hyades open cluster: 51 Tau, V818 Tau, and
$\theta^2$ Tau. The choice of these objects is discussed and a statistical
method is described and applied to the colour-magnitude diagram (CMD) of the
selected stars, giving rise to contour levels in the metallicity-age plane. The
effects of the Hipparcos parallaxes on these confidence regions, with influence
on both age and metallicity, are studied for the V818 Tau system through a
comparison with very accurate but older orbital parallaxes. Finally,
theoretical simultaneous age-metallicity estimates are given for the three
binaries and compared with observational constraints.
