Card Grading Standards
How PSA, BGS, and AgentGrail AI evaluate a card — the four criteria, the centering tolerance table, and exactly what each letter grade means.
The Four Grading Criteria
PSA, BGS, and SGC all evaluate the same four attributes. AgentGrail measures all four for the scorecard, but as of SCRUM-4500 (2026-07-07) only corners is verified accurate enough from a head-on phone photo to cap AgentGrail's own displayed grade — centering, edges, and surface are shown as diagnostics only.
The distance between the printed image and each card edge. PSA measures left/right and top/bottom independently. Shown for reference on the scorecard — as of SCRUM-4500, AgentGrail's OpenCV centering signal doesn't reliably track PSA truth from head-on photos, so it does not cap the displayed grade.
The sharpness of all four corners under 5× magnification. Wear shows as fraying, rounding, or white specs (chipping). Corners is the only sub-criterion that currently caps AgentGrail's displayed grade — if the corners signal says the card is a C, the badge shows C even if the overall verdict looked higher.
The four straight edges of the card. Nicks, chips, or roughness along the cut line signal wear. Shown for reference — as of SCRUM-4500, AgentGrail's OpenCV edges signal runs backwards vs verified truth, so it does not cap the displayed grade.
Scratches, print lines, stains, and gloss consistency on both faces. Head-on phone photos rarely capture surface defects — raking light at an angle is required. AgentGrail marks surface N/A on standard photos and does not use it to cap the displayed grade.
PSA, BGS, and SGC each weight the four criteria in their own published (and partly proprietary) formulas — AgentGrail does not attempt to reproduce those weights. Corners was verified against 947 BGS-graded reference pairs (docs/research/2026-07-07-opencv-percriterion-vs-bgs.md) to actually track real grading outcomes; centering and edges were verified to NOT.
Grade Scale — A through E
AgentGrail maps PSA's 10-point scale to five letter bands. The letter badge you see on every card comes from the grail-head verdict, capped down if the corners sub-score signals a worse grade (see "How AgentGrail AI Scores a Card" below). The centering column is PSA's own published reference ceiling, shown for context — it is not something AgentGrail measures or caps on.
| Letter | PSA Equivalent | PSA centering ceiling (reference) | What it means |
|---|---|---|---|
| A | PSA 10 — Gem Mint | 60/40 | Perfect or near-perfect. Virtually no wear visible at 5× magnification. |
| B | PSA 9 — Mint | 65/35 | One minor defect allowed — slight corner wear or minor print dot. Still investment-grade. |
| C | PSA 8 — Near Mint–Mint | 70/30 | Very light corner wear or a minor surface imperfection. Solid collectible. |
| D | PSA 7 — Near Mint | 75/25 | Slight rounding on one or more corners. Still presentable and well-centered. |
| E | PSA 6 or below | 80/20+ | Visible defects on multiple criteria. Typically not worth grading fees unless the card itself is rare. |
Centering Tolerance Table
PSA published standards / reference only — not an AgentGrail grade cap.
This table shows PSA's own published centering tolerances, for context on what professional graders look for. AgentGrail displays a centering score on every card's scorecard, but as of SCRUM-4500 (2026-07-07) that score is diagnostic only — verified against 947 BGS-graded reference pairs to not reliably track real grading outcomes from a head-on phone photo, so it does not cap AgentGrail's displayed grade.
| L/R or T/B ratio | Centering score | PSA reference tier |
|---|---|---|
| 55/45 or better | ≥ 90 | PSA 10 safe zone |
| 60/40 | 80 | PSA 10 floor (SCRUM-4130) |
| 65/35 | 70 | PSA 9 floor |
| 70/30 | 60 | PSA 8 floor |
| 75/25 | 50 | PSA 7 territory |
| Worse than 75/25 | < 50 | PSA 6 or below |
Centering thresholds follow PSA's published standards. The 60/40 floor for PSA 10 was aligned in SCRUM-4130 (2026-06-17) after cross-referencing the official PSA grading page. Prior versions used a 55/45 floor that was too strict.
How AgentGrail AI Scores a Card
- 1Photo quality gate — AgentGrail first checks if the photo is usable — blur, glare, sideways cards, and busy backgrounds trigger a coaching prompt rather than a grade. A bad photo → bad grade is a false negative we actively try to avoid.
- 2CLIP image embedding — The card photo is encoded into a 512-dimensional visual vector by a CLIP ViT-B/32 model trained on hundreds of millions of images. This captures overall visual condition beyond what rule-based scoring can see.
- 3Per-criterion sub-scores — OpenCV measures centering, corners, edges, and surface, producing 0–10 scores for each — shown on the scorecard for transparency. As of SCRUM-4500 (2026-07-07), only corners is verified to track real grading outcomes from a head-on photo; centering, edges, and surface are diagnostics only and never affect the displayed grade.
- 4Grail head verdict — A neural-network classifier turns the 512-d CLIP image vector into a single BUY / PASS / REVIEW probability. None of the per-criterion sub-scores are inputs to this head — it sees only the image embedding. This head is trained on thousands of labeled cards across sports and eras.
- 5Conservative reconciliation — The displayed letter grade is the grail head's verdict, capped down if the corners sub-score signals a worse grade — corners is the only sub-criterion currently permitted to do this. When fewer than two sub-criteria are reliably measurable, AgentGrail shows "not graded" rather than a single-axis number dressed up as a composite.
Grader Comparison
PSA, BGS, and SGC use the same four criteria but differ in subjectivity and labeling.
| Grader | Top grade | Sub-scores shown? | Notes |
|---|---|---|---|
| PSA | PSA 10 Gem Mint | No | Most liquid market. Highest premium per PSA 10. Population report available via PSA API. |
| BGS | BGS 10 Pristine / Black Label | Yes — on label | Shows centering/corners/edges/surface separately. BGS 9.5 ≈ PSA 10 in many markets. Stricter surface standards. |
| SGC | SGC 10 Pristine | No | Fast turnaround, popular for vintage. SGC 10 trades at a discount to PSA 10 for modern cards. |
| AgentGrail | A (PSA 9-10 candidate) | Yes — in drawer | Prediction only — not an official grade. Calibrated to PSA outcomes on a labeled training set. |
Not investment advice
AgentGrail AI provides condition estimates to help collectors make informed decisions. We are not a grading company and our AI predictions are not official grades. Always verify with a professional grader before making significant purchases. Past model performance does not guarantee future accuracy.
PSA® is a registered trademark of Collectors Universe, Inc. Beckett Grading Services (BGS®) and SGC® are independent companies. AgentGrail has no affiliation with any grading company.