Interpretation: This code corresponds to a protruding head rivet (likely a universal head type). The diameter code of 5 gives a diameter of 5 × 1/32 inch = 0.15625 inch (approximately 5/32 inch). The "F" indicates the manufactured head is to be installed on the far side of the assembly. The blank lower left quadrant confirms that no countersinking or dimpling is required (consistent with a protruding head rivet). The length code of 8 corresponds to the designated grip length.
100° countersunk flush head rivets, used on external aircraft skins to reduce drag.
Expressed in 1/16-inch increments. In 4-6 , the 6 means 6166 over 16 end-fraction 38three-eighths Key Rivet Materials and Standard Part Numbers
