What a Grade Measures
Grading is an opinion about condition, recorded on a ten-point scale and sealed inside a tamper-evident holder. Four qualities drive almost every score. Centering measures how evenly the borders sit around the image on the front and the print on the back. Corners are checked for wear, softness, and any rounding. Edges are inspected for chipping and print roughness. Surface covers scratching, print lines, and gloss loss.
A card that leaves the factory perfect can still grade a nine because one border is a hair thicker than the other. That is the point of grading: it turns a subjective argument about condition into a number two buyers can trade on. It does not make a common card rare, and it does not predict whether a player will stay healthy or stay in the lineup.
The Grading Companies
PSA
Professional Sports Authenticator is the largest grading company in the hobby and the standard most buyers compare against. Its ten-point scale with half grades is widely understood, and PSA-graded cards usually command the strongest resale prices. Turnaround times and fees vary by service level, and the population report is public, which matters when you are judging how rare a high grade really is.
BGS
Beckett Grading Services issues a 1 to 10 grade made of four subgrades: centering, corners, edges, and surface. The transparency of those subgrades makes BGS popular with collectors who care about why a card scored what it did. A BGS 9.5 with strong subgrades is a premium card, and the rare BGS 10 sits above it.
SGC
SGC is known for fast turnaround and a tuxedo-style black holder that photographs well. Its grading is generally considered consistent, and vintage collectors often prefer SGC because of how it treats older cards and centering tolerances.
Raw cards
Ungraded cards are cheaper and leave the grading decision to you. That is a real advantage if you enjoy the process, and a real risk if you are buying sight unseen. Inspect photos closely for corner wear, surface scratching, print lines, and centering before you pay a graded-card price for a raw card.
Is a Graded Card Worth It?
Run the numbers before you pay a premium. Look up recent sold prices for the same card in the same grade, then compare them with raw copies of the same card. If the graded sale is far above the raw sale plus grading fees and shipping, the slab is priced for convenience and you are paying for certainty. If the gap is small, you are buying an authenticated card at close to raw money, which is usually the better end of the market.
Population counts matter too. A grade nine of a heavily submitted card is ordinary, while a nine of a card that is famously off-center is genuinely tough. Buy the card you want in the grade you can afford, and treat a high grade as a bonus rather than the reason the card exists.
Buying Slabs Safely
Check the cert number against the grading company's lookup before you buy, and confirm the label matches the card in the case: player, year, set, parallel, and grade. Look for cracks, scuffs, or resealed edges in the holder itself, and read the photos at full size rather than trusting a thumbnail.