This smart calculator pin badge displays the mysterious and significant number 0.7734. Nobody really knows what this number means (until you turn your calculator upside down, at which point it just says 'Hello').
Enamel pin badge measures 2.4cm by 3cm, with a single pin fixture on the back (so you can spin it upside down while it's pinned on to things). Design by Jamie Gallagher, who also sells a selection of other fun scientific pin badges.
Price = p118 pence = £6.47