This is the water pipe adapter union from a Cologne V6 inlet manifold. Fits on front passenger side of inlet low down (beneath the top main water housing) and joins the bypass hose that drops down to the back of the thermostat housing rear cover.
Found on most 2.3 and 2.8 Cologne V6 inlets, carbed, or injected - Capri, Granada, Cortina, Sierra.