SWSH12: Silver Tempest Forest Seal Stone #156: PSA 9 vs PSA 10

The PSA 10 to PSA 9 spread on SWSH12: Silver Tempest Forest Seal Stone #156 is one of the widest gaps in vintage WOTC: $42, with PSA 10 copies trading at 6.2x a PSA 9. Based on the most recent PSA 10 sale of $50.00 on May 1, 2026, the math leans toward holding the 9: expected value turns negative at conservative upgrade probabilities once the resub fee is in.

SWSH12: Silver Tempest Forest Seal Stone #156 Holo

PSA 10

$49.86

Last sale $50.00 on May 1, 2026 UTC

PSA 9

$8.00

Last sale $8.00 on Dec 3, 2025 UTC

PSA 8

$1.00

Last sale $1.00 on Aug 5, 2025 UTC

The Spread

The PSA 9 to PSA 10 spread on Forest Seal Stone #156 SWSH12: Silver Tempest.

$42

Dollar gap, PSA 9 to PSA 10

6.2x

PSA 10 sells for 6.2x a PSA 9

Three-Outcome EV Calculator

PSA 9 acquisition cost ($)

PSA resub cost ($)

Probability of each outcome (must total 100%)

PSA 10 (upgrade) 15%

PSA 9 (regrade) 70%

PSA 8 (downgrade) 15%

Defaults are conservative starting points. Adjust based on the specific slab. A borderline 9 with strong centering plays differently than a 9 with edge wear.

PSA 10 outcome (sale price minus resub minus acquisition) $0

PSA 9 outcome (regrade, no upgrade) $0

PSA 8 outcome (downgrade, slower sell, tied capital) $0

Expected Value

Math favors holding the 9

SWSH12: Silver Tempest #156 Forest Seal Stone Holo released in 2022 sits in the vintage WOTC tier where gem-mint premiums above $42 are common. PSA 10 populations shrink faster than supply on cards of this era, which is why the upgrade arbitrage stays alive.

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