A group of 13.
It was commonly called "the long measure".
The cardinal number that is the sum of twelve and one.
By 1864 Hotten's Slang Dictionary gives the definition for Baker's dozen:
"This consists of thirteen or fourteen; the surplus number, called the inbread, being thrown in for fear of incurring the penalty for short weight."
Give me a baker's dozen of candies.
The situation changed with a baker's dozen of minutes.
I found a baker's dozen of gold coins under the tree.