The original template for this one-weight, all-caps font was the inscription on Trajan’s Column, carved in AD 113 to celebrate the emperor Trajan’s victory in the Dacian Wars. College student Jason Smith copied the stone lettering from the cast on display in London’s Victoria & Albert Museum.
In Roman times, the signmaker would paint letters onto stone with a wide brush for the stone mason to chisel out later. The signwriter would end each stroke with a flick of his brush, which the mason would also carve into the stone.
Ecce (as they would have said in Rome): the serif was born.