TAG vs PSA centering
Both ask for 55/45 on the front for a 10. The difference is in how the ratio is read, and in the back.
Side by side
| PSA | TAG | |
|---|---|---|
| Front, for a 10 | 55/45 | about 55/45 |
| Back, for a 10 | 75/25 | about 65/35 (trading cards) |
| Front, for a 9 | 60/40 | about 57.5/42.5 in TAG's rubric |
| A top grade above 10 | None | 10 Pristine, about 51/49 front and 52/48 back |
| Half grades near the top | None above 9 | No 9.5: TAG's 10 starts where others split 9.5 and 10 |
PSA's figures are from its published grading standards; TAG's are from the rubric TAG publishes, which gives them as approximate.
TAG reads further off centre than a ruler
TAG measures centering by machine and reports it to two decimals. Its reports put the same card further from 50/50 than a measurement of the printed borders does, most of all left to right on the front. So a card that measures 54/46 with a ruler can be past 55/45 in TAG's reading.
Preslab measures the borders, then converts its reading to the way TAG reads a card before comparing it with TAG's limit. That is why the TAG row on a result can say "Not a 10" when the PSA row says "Clear".
The back matters more at TAG
PSA lets a 10 have a back as far off as 75/25. TAG asks for about 65/35 on a trading card's back. A card with a clean front and a back at 70/30 can be a PSA 10 on centering but not a TAG 10.
Which to choose
Centering is one of four things a grade weighs, with corners, edges and surface. Preslab measures only centering, and says how high it lets the card grade at each company. Look at the corners and edges yourself before you decide where to send it.
Preslab is not affiliated with PSA, TAG, BGS, CGC or ACE.