This is a pair (two) or engine mounts to fit many Jaguar saloons and sports cars of the 1950s and 1960s, including Mark I and Mark 2, 3.4S and 3.8S, 420, XK120 (late), XK140, XK150, E-type and others. The Jaguar part number is C4784.
This mount is also used for the rear bumper of most Jaguar saloons of the 1960s. Mark I and 2 models used four of these; we think the big Mark X saloons used two (not sure, though).