Stamps and received marks
Received stamps were not part of the blank form, but many forms were clearly designed around them. A blank box near the top right often means "stamp goes here" whether or not anyone printed that instruction.
Mark sample sheet
Red received stamp, black file stamp, blue initials, correction-fluid ridge, and two-hole punch spacing.
Stamp overlap
Stamp pads dry unevenly. The date may be clear while the office name is only a rectangle.
Correction marks
Correction fluid scans as a pale ridge when light hits from the side. Flatbed scans hide some of it.
Placement
A good form leaves stamp space without saying so. A bad one puts the signature line exactly where the stamp lands. Completed copies show this better than blanks.