Methodology

1. How we value cards

Every value is a comparable-sales estimate — built from actual recent sales of the same card at the same grade, never from a list price or an opinion. For each graded card we resolve its identity by its grading cert, then aggregate real closing prices across the major marketplaces — eBay, REA, Fanatics Collect, and Huggins & Scott — over roughly the trailing 90 days, weighted toward the most recent and most similar sales.

• Confidence reflects evidence. Cards with many recent comparable sales carry a higher-confidence value; thinly traded cards carry wider uncertainty, and we say so.
• Independent, redundant data. Market data comes from our pricing partner (CardHedge), with a second independent graded-comp source as an automatic fallback — so a single provider outage doesn’t leave a collection unpriced.
• Graceful degradation. If live data is briefly unavailable, we show the most recent known value, clearly labeled “as of” its date — rather than guessing.
• Nothing is fabricated. Cert numbers, population data, and sale prices are real or they’re left blank. We never invent a value or a cert to fill a gap.

2. The Slabline Score (0–1000)

The Slabline Score measures how well-protected a collection is — not how good the cards are. A pristine collection that’s uninsured and concentrated in one card can score lower than a modest, well-managed one. It’s a weighted blend of five factors, each scored 0–100:

• Insurance — 35%. Coverage relative to current market value, discounted by how stale the latest appraisal is.
• Concentration — 25%. Exposure to a single card: a larger top holding as a share of total value lowers the score.
• Storage — 20%. Self-reported protections — climate control, fire, theft, light — plus handling discipline.
• Liquidity — 10%. How readily holdings convert to cash at predictable prices, value-weighted across the collection.
• Provenance — 10%. Share of cards with a verified grading cert, plus documentation depth.

The five sub-scores combine on their weights into a 0–1000 composite, which maps to a letter band:

• A — 880+ · Excellent
• B — 750–879 · Strong
• C — 600–749 · Fair
• D — 400–599 · At Risk
• F — below 400 · Poor

Every score is stamped with a model version and recomputed whenever the collection, its inputs, or the market changes, so the number on screen always reflects current data.

3. Grading & liquidity decisions

Beyond a value, Slabline turns the same data into decisions no price guide answers:

• How the same card grades at each company. Grading standards differ — BGS is capped by its weakest subgrade and weighted on centering, SGC is tough on centering, CGC a touch more forgiving on surface. Pre-Grade applies each company’s known tendencies to the card’s own subgrades (centering, corners, edges, surface) to estimate what PSA · BGS · SGC · CGC would each likely give it, then reads the value ladder at each of those grades to show which company nets the most for that specific card. Deterministic and explainable — not four numbers guessed by a model, and not a promise of the outcome.
• Expected grading profit. The card’s real grade distribution (gem rate & population) weights the value ladder into a probability-weighted expected value, minus the raw value and an estimated grading fee. Because the graded population skews toward better copies, we present this as an optimistic ceiling, not a promise.
• Liquidity & recovery. Dealer buy-vs-sell spreads estimate what a fast sale actually returns versus market value — the gap is liquidity risk, and it feeds the Liquidity factor of the Score.

4. Data sources & integrity

Card identity and population data come from the grading services (PSA · BGS · SGC · CGC ) and their public records where available; valuations from the comparable-sales sources above. Insurance and storage details are self-reported by the collector — they drive the Insurance and Storage factors and are not independently verified by Slabline. We hold ourselves to a simple rule: real data or no data — we do not estimate a cert, a population, or a sale that didn’t happen.

5. Platform statistics — how we count

The figures shown across the site (for example on the home page) describe the catalog Slabline tracks, not any one collection. Each is defined precisely so a larger number never overstates what it measures:

• Graded cards tracked — the count of distinct cards in our catalog (one entry per card and grade we can serve a page for), whether or not we currently hold a live value for it.
• Live market values — the subset of those cards for which we currently hold a value: a comparable-sales estimate, a price-guide figure, or — for cards with no graded market — a raw (ungraded) price. A card counts once, at its headline grade.
• Tracked value, daily — the sum of those headline values. It counts one grade per card (the card’s own grade), so it is a conservative floor, not a market size.
• Tracked across all grades — a different, larger figure: for every card that has a full price-by-grade ladder, we sum the price of each priced grade rung (PSA 10, 9, 8, … and raw). It is the total of the per-grade market prices we track, and we label it distinctly from “Tracked value” so the two are never conflated. It is not a claim that a slab exists at every grade, and not a market capitalization — it does not multiply by how many copies have been graded.
• Raw (ungraded) — when a card has no graded market (common in trading-card games), the only honest price is its loose, ungraded value. We show that figure clearly labeled “Raw (ungraded),” and it is never presented as the value of a graded slab.
• Market capitalization tracked — the estimated total value of every graded copy in existence for the cards we track: for each card we take its price-by-grade ladder and multiply each grade’s price by how many copies have been graded at that grade (population from the grading services’ public reports), then sum. A copy is valued at the price of the highest priced grade at or below its own — never rounded up to a grade we don’t price. Each card’s population is counted once, however many grade pages it has. A price above $10,000 a copy is used only where that card has a recorded sale at that grade; otherwise the copy is valued from the nearest lower grade that has sold, or left out. This is the one figure that reflects quantity, so it is far larger than the per-card figures above; it is an estimate of market size, not the value of any collection.

Every rung and price above is sourced — a price-guide figure or an observed sale — never a fabricated grade multiple. Cards with no priced rung contribute nothing rather than an estimate.

Coverage. The market-capitalization figure is computed only over cards for which we hold both a full price ladder and current population data, and it names the number of cards it spans. As population coverage grows, the figure grows with it — it is a tracked subset of the hobby, never a claim about the entire market.

Coverage, independently checked. We also measure how much of the graded-card market the catalogue covers against an outside benchmark: the public index constituents of Card Ladder (CL50, SX100, Bowman 100, Gongshow 100, TCG83, Culture51 and the category indexes), matched to Slabline card pages and weighted by market value × recorded sales. As of 2026-08-25: 96.5% of graded-card dollars traded across 1,409 sampled printings, and 98.1% across Baseball, Basketball, Football and Pokémon. The remainder is mostly cards with no published guide price (patch autographs, pre-war oddballs), which we deliberately don't list rather than guess at.

Freshness. Of the cards carrying a live value, 738,875 were re-observed in the last 30 days and 382,551 in the last 10 — the rest hold their most recent guide price until the next observation. We publish this so “priced live” is a measurable claim, not a slogan.

6. Limitations

Values are estimates, not guarantees. Card markets are volatile and can move sharply; thinly traded cards are inherently less certain; and a comparable-sales estimate is not a substitute for a certified appraisal or an underwriter’s review. Confirm any value with a qualified appraiser and your insurer before relying on it for insurance, sale, or financial decisions. The Slabline Score is a directional risk indicator, not financial or insurance advice.