From Lost Temple Traders:

"We’re all a little mad! Introducing the Zombie Hatter Mug designed for Lost Temple Traders by Bridget McCarty. The Zombie Hatter stands 6” tall, and is limited to 300 pieces. Shipping starts end of week.

Produced by Munktiki Imports."

The hat has "10/6" written on it. The 10/6 refers to the cost of a hat — 10 shillings and 6 pence, and later became the date and month to celebrate Mad Hatter Day.