From early Anglo-Saxon times the shilling was a unit of account, that is to say, a value used in calculations which had no corresponding coin. Its value became established as equivalent to 12 pence and there were 20 shillings to the pound.
The shilling as a coin was introduced at the beginning of the 16th century during the last years of the reign of Henry VII and until the middle of that century was known as a testoon. It was one of the first English coins to bear a real portrait of the monarch instead of the representative portrait which had served for the previous ten centuries; and it was for this reason that it derived its name of testoon from the Italian Testone or Headpiece introduced in Milan in 1474.
Convenient in size and value, the shilling became one of the popular workhorses of the silver circulation. Colloquially described for some unknown reason as a bob, it was not superseded until 1968, during the preparations for decimalisation, when issues began of the new 5p piece. Even then, being the exact decimal equivalent of 5p, they continued to circulate alongside 5p pieces until 1990, when they were finally demonetised.