The kings, sitting on ornate thrones with swords across their laps, seem lost in thought, their shoulders weighed down by their preoccupations. The queens, also enthroned, have their hands clapped to their cheeks as if in dismay and thinking, “D’oh!” But Mr. Robinson observes about the pieces in general, “Identifying the exact nature of their attraction for people of the time is a challenge,” and so the humor question remains unanswered.

What is known about the chessmen is that they were found by a farmer on the Isle of Lewis, the largest island of the Outer Hebrides, in 1831. How they got there is a mystery. Some think they arrived from Iceland, but conventional wisdom has it that they somehow came off a merchant ship traveling a regular trade route between Norway and Ireland and that they were produced in Trondheim, a Norwegian town, between 1150 and 1200.

Image A warder, or a rook. Credit... Karsten Moran for The New York Times

The hoard included 78 chessmen from at least four different, incomplete sets; some pieces resembling checkers; and a belt buckle carved from ivory. The British Museum quickly acquired most of them, and in 1888 the National Museum of Scotland, Edinburgh, secured 11 that had remained in private hands.