A set of brass plates defining Imperial standards for measurement of length, and a large clock, set on brick wall to the right of the main entrance to the Observatory, facing outwards. Also shown is the height above sea level and the Ordnance Survey Benchmark. The work features the 'Shepherd Clock' – large round 24–hour clock set on a black surround of painted metal fastened to the wall. It has 23 Roman numerals round the face and a zero at the top with decorative hands. Five-minute intervals are marked in Arabic numerals round the outer edge, and there is a small minute dial above the centre. Three grey plastic plates in a row beneath give information about the standards. The left one is about the clock and time ball. The middle one shows height above mean sea level at Newlyn.