I have two $2.00 bills that are dated 1976. On one of them my grandfather wrote at the bottom 4-13-1976 1st issue. I will call this one A. The issuing bank is a "G" on banknote A with the serial number G12037878A. In the upper left corner across from the 7 is B4 and on the right bottom hand side is B17. What do these mean? The other$2.00 bill has an "F" on it with the serial number F28836375A, the letters by the 6 are B1 and B29. Are either of these bills worth anything. They were never used and are crisp and clean. Thank you.