The three woman on the back of this coin stand for the three types of metals that were used for coins.

One of the ladies stood for Bronze. This metal was used for the common coins of their day - something like our pennies.

The smallest size Bronze coin was mentioned in the section of the Gospel that speaks about the Widow's Mite.

Silver is more precious than Bronze and was used for major payments like a full day's pay. 

When you read the parable of the worker in the vinyard it says they were paid a full day's wage - which would have been a silver coin like this.

Gold was the most precious of the metals and was used for major government payments.