In this paper, we design the optimal procurement mechanisms when bidders are
privately informed on efficiency and on observable but neither verifiable
nor contractible quality. We show that most of the optimal procurement
institutions are mixed procedure implying both separation and pooling. Thus,
the existing take-it-or-leave-it offers and procurement auction appear only
as polar cases. Moreover, we show that separation and pooling may affect the
allocative efficiency of the procurement in a counterintuitive way, such
that a less bunching mechanism can be a more inefficient one.