a) The outer line of the left frame is visible opposite leaf 2. It disappears below leaf 2. As a result, the frame is thin from the middle of leaf 1 to the bottom of the 2. It is thicker from the bottom of the 2 to the corner due to retouching.

b) Horizontal lines in the LL spandrel are weak.

c) Vertical line of the LNB was retouched from just below the top to just above the bottom. It gets thicker from top to bottom.

d) Bottom of the left frame is retouched. It touches the bottom frame, but stops short of the bottom corner.