Long Sword +3

Long Sword +3 is an enchanted weapon which can inflict 1d8 +3 points of slashing and it has -3 THAC0 bonus. The weapon weighs 2 lbs and it has a speed factor of 3. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. Jamis Tombelthen, a NPC encountered during the Ranger - Protector of the Umar Hills stronghold quest, drops this.

In Throne of Bhaal, it's for sale at the Tankard Tree and Carras and Karthis al-Hezzar sell this weapon.

In-game description
"These swords are usually referred to as doubled-edged swords, war swords, or military swords. The blade hums slightly in your hand, the only overt evidence that magic runs through it."