  We show that quark models of current matrix-elements based on the
Bakamjian-Thomas construction of relativistic states with a fixed number of
particles, plus the additivity assumption, are covariant in the heavy-quark
limit and satisfy the full set of heavy-quark symmetry relations discovered by
Isgur and Wise. We find the lower bound of $\rho^2$ in such models to be $3/4$
for ground state mesons, independently of any parameter. Another welcome
property of these models is that in the infinite momentum limit the wave
functions vanish outside the domain $0\le x \le 1$.
