Known as Queen Mary’s Dial, this has been called the finest example of its facet head class. It takes the form of a sandstone prism standing on its point, with 20 triangular facets elaborately carved with coats of arms and monograms of King Charles I and his Queen Henrietta Maria. There are various bowl, heart and triangular sinkings with dials. In some the gnomon is the nose of a carved face, in others it is an open fret worked metal plate. The top of the pedestal is an inverted hemisphere above a square column decorated with acanthus leaves and mounted on three high spreading octagonal steps.
The steps are probably later than the dial, which is dated 1633 and was made for the Scottish Coronation of Charles I by John Mylne III, Master Mason to the King. Royal Accounts show that it cost £408 15s 6d (Scots) plus further charges for painting and gilding, illustrating that at the time it was customary to paint these stone sculptures.