How a StopperLab estimate is made

The scale

Centering is measured from the photos as the larger share of the border on the worse axis, and compared with the published 1 to 10 scale's tolerances:

• front: 55/45, 60/40, 65/35, 70/30, 80/20, 85/15, 90/10
• back: 75/25, 90/10

Uncertainty

Every measurement is shown with its uncertainty (±u). An estimate is a range of grades that holds the card's grade about four times in five; a range that would span more than three grades is not given.

Confidence levels

• ◆◆◆ High: every criterion assessed, a calibrated range of one or two grades.
• ◆◆◇ Medium: centering, corners and edges assessed, a range of at most two grades.
• ◆◇◇ Low: a trial range, a range of three grades, or a criterion not assessed.
• ∅ Not assessable: no estimate is given.

Until enough cards have been verified, every range is a trial range at low confidence, and chances are shown as words (unlikely, possible, likely), never as numbers.