A student paid his lab fee today in 10 $1 bills. I noticed that five looked rather old, and different. I looked at the and they were series 1957, 1957 A, and 1957 B Silver Certificates. One of the 1957a bills has a star at the start of the serial number instead of a letter. Are these worth anything and do i need to check with his parents and make sure he hasnt accidently taken someones dollar collection.