In October 1986 a bunch of computer geeks came together in Boulder, Colorado to celebrate shared silliness inspired by the iconic illustrations of Alice In Wonderland’s Mad Hatter.
Such was its popularity that within two years official status was afforded for the day. It marks the most notable of John Tenniel's 92 shaded outline illustrations of Lewis Carroll's nonsensical creations, who people the 1860s classics Alice's Adventures in Wonderland, Alice Through the Looking-Glass and What Alice Found There (here illustrated by 2010 Disney/Burton/Depp Mad Hatter's Tea Party magic).
The 10/6 States-style date doffs a cap to the Mad Hatter's headwear bearing the note “In This Style 10/6”.
The phrase "mad as a hatter”, meanwhile, derives from the mercury used in the production of felt, which caused milliners to develop dementia.
On a lighter note, try our madcap Carroll character quotes quiz.
For the record, the final question answer is "because it can produce a few notes, though they are very flat; and it is nevar (sic) put with the wrong end in front." Curiouser and curiouser!