  We establish an orientifold Calabi-Yau threefold database for $h^{1,1}(X)
\leq 6$ by considering non-trivial $\mathbb{Z}_{2}$ divisor exchange
involutions, using a toric Calabi-Yau database
(http://www.rossealtman.com/toriccy/). We first determine the topology for each
individual divisor (Hodge diamond), then identify and classify the proper
involutions which are globally consistent across all disjoint phases of the
K\"ahler cone for each unique geometry. Each of the proper involutions will
result in an orientifold Calabi-Yau manifold. Then we clarify all possible
fixed loci under the proper involution, thereby determining the locations of
different types of $O$-planes. It is shown that under the proper involutions,
one typically ends up with a system of $O3/O7$-planes, and most of these will
further admit naive Type IIB string vacua.The geometries with freely acting
involutions are also determined. We further determine the splitting of the
Hodge numbers into odd/even parity in the orbifold limit. The final result is a
class of orientifold Calabi-Yau threefolds with non-trivial odd class
cohomology $h^{1,1}_{-}(X / \sigma^*) \neq 0$.
