Weak semi-circular mark in bottom left corner

a

No marks in top left corner

No mark in bottom left corner

No mark in bottom left corner

Weak mark in top left corner - no mark in top right corner

a

No mark in top left corner

No marks in bottom corners

No mark in top right corner

No mark in bottom left corner

No mark above slot on left ridge

No mark near center on bottom ridge

No marks above slot on right edge

No marks in any corner

c

No mark above slot

No mark on bottom ridge

b

No line at 10-o'clock of stud 4

No mark on bottom ridge

b

No marks between stud 1 and 3, and between 2 and 4