Sashenstar's Ruby Ring is the property of a dead noble who was a daughter of house Sashenstar. It is found during the quest Missing Citizens after killing the Ogre Mage, and is required to get an extra 3000 GP bonus as part of the quest reward.
I'ts image is identical to a standard Ruby Ring.
Scar will not accept a normal Ruby Ring for the extra reward.
As of at least version 2.0 of Baldur's Gate: EE, there are no longer female bodies in the sacs, and the ring is found on the Ogre, not in the sacs.