Iron Age IIC 700-586 BCE
The Philistine occupied the coastal Levant 1150-8th century BCE so the weight of a pim during this period of the Judges could be an anachronism to the time of King Saul 1000BCE or 8th century BCE time of Hezekiah.
A number of specific weights are mentioned in the Old Testament
Exodus 38:26 beka 6.33g
I Samuel 13:21 pim 8.1g
Nehemiah 10:33 shekel 11.3g
Guide to Biblical Coins David Hendin