Lochranza Castle is at the north-west corner of Arran (opposite Skipness). It dates back to the 13th century although much of the visible remains date to the 16th. The castle is in the care of Historic Scotland and contains a number of Ministry signs.
Unlike other sites in Scotland where there are the distinctive Ministry signs (e.g. Kilberry, Kilmory, Kilmartin) these metal signs at Lochranza are more like information panels. See the example at Kingarth on Bute. They have, however, stood the test of time (and weather) unlike some of the more modern information panels.