Strength Charm boosts an attached Pokémon's attack by 10 damage before it discards itself. The Expedition and Team Magma vs Team Aqua wordings applied the bonus after Weakness and Resistance. Team Magma vs Team Aqua also limited the bonus to damage against the Active Pokémon and added a clause discarding the card if the holder is Knocked Out. The Deoxys wording moved the bonus to before Weakness and Resistance and discards the card at the end of the turn the holder attacks.
Strength Charm debuted in the WOTC era's Expedition Base Set with art by Keiji Kinebuchi, then was reprinted in the EX era across Team Magma vs Team Aqua and Deoxys with the same artwork, before Dragon Frontiers brought new art by Shizurow and a minor rewording, the attack becoming this attack. Our catalog lists 4 printings.
The Deoxys printing's rewording brought the card in line with an errata that had already been issued for it.
The Expedition Base Set printing is Strength Charm's first release, applying its bonus after Weakness and Resistance
The Deoxys printing reworded the timing of the bonus damage to align with a prior errata
The Dragon Frontiers printing carries new artwork by Shizurow
The Expedition and Team Magma vs Team Aqua wordings apply it after Weakness and Resistance; the Deoxys wording onward applies it before.
The earlier wordings discard it at the end of the turn its bonus applies, the Deoxys wording onward at the end of the turn the holder attacks, and the EX era wordings also discard it if the holder is Knocked Out.
From Expedition Base Set (2002) · 1 printing
Attach Strength Charm to 1 of your Pokémon that doesn't have a Pokémon Tool attached to it. Whenever an attack from the Pokémon that Strength Charm is attached to does damage (after applying Weakness and Resistance), the attack does 10 more damage. At the end of your turn in which this happens, discard Strength Charm.
From Team Magma vs Team Aqua (2004) · 1 printing
Attach Strength Charm to 1 of your Pokémon that doesn't already have a Pokémon Tool attached to it. If that Pokémon is Knocked Out, discard this card. Whenever an attack from the Pokémon that Strength Charm is attached to does damage to the Active Pokémon (after applying Weakness and Resistance), the attack does 10 more damage. At the end of the turn in which this happens, discard Strength Charm.
From Deoxys (2005) · 1 printing
Attach Strength Charm to 1 of your Pokémon that doesn't already have a Pokémon Tool attached to it. If that Pokémon is Knocked Out, discard this card. Whenever an attack from the Pokémon that Strength Charm is attached to does damage to the Active Pokémon, the attack does 10 more damage (before applying Weakness and Resistance). Discard Strength Charm at the end of the turn in which this Pokémon attacks.
From Dragon Frontiers (2006) · 1 printing
Attach Strength Charm to 1 of your Pokémon that doesn't already have a Pokémon Tool attached to it. If that Pokémon is Knocked Out, discard this card. Whenever an attack from the Pokémon that Strength Charm is attached to does damage to the Active Pokémon, this attack does 10 more damage (before applying Weakness and Resistance). Discard Strength Charm at the end of the turn in which this Pokémon attacks.

Strength Charm
Pokémon Tool
First printed in Expedition Base Set (2002)
Attach Strength Charm to 1 of your Pokémon that doesn't already have a Pokémon Tool attached to it. If that Pokémon is Knocked Out, discard this card. Whenever an attack from the Pokémon that Strength Charm is attached to does damage to the Active Pokémon, this attack does 10 more damage (before applying Weakness and Resistance). Discard Strength Charm at the end of the turn in which this Pokémon attacks.