This item can not be made using the Crafting skill.
Players may wear the necklace during the quest. Players cannot obtain it after they complete the quest.
Players can get this item after the quest however by dropping the necklace outside of the gate of the manor and then completing the quest and then simply running back outside the gate to pick it up. Note: if you have already completed the quest you can not get another.
The only way to keep it is to drop it and take another one during the quest, and drop the second one right before you complete the quest and then pick it up again after the quest. The guard will take it away regardless of if it is floured and/or wielded, how many you are carrying or who the murderer is.
Note that banking it before finishing does not work either.
This necklace appears to be a brass necklace with silver plating. Players can see the sides of the necklace are the same colouring as a brass necklace and the gem is the same colour as well for both necklaces. The examine text seems to support this. This makes the silver necklace appear to have a brass 'trim'.
The necklace only takes this appearance when playing with a male avatar. Otherwise, the necklace is completely silver for female avatars.