Note for young people and Americans.

Two farthings = One Ha'penny
Two ha'pennies = One Penny
Three pennies = A Thrupenny Bit
Two Thrupences = A Sixpence
Two Sixpences = One Shilling, or Bob
Two Bob = A Florin
One Florin and One Sixpence = Half a Crown
Four Half Crowns = Ten Bob Note
Two Ten Bob Notes = One Pound (or 240 pennies)
One Pound and One Shilling = One Guinea

The British resisted decimalized currency for a long time because they thought it was too complicated.