The Silver Hilt is a part of the Silver Sword.
Location
If you have the Silver Blade when you return to Athkatla in Chapter 6 and go to one of the major locations in the city, you will run into a githyanki named Kruin. He will demand that you hand over the Silver Blade. You can either give it to him or decide to fight him and his friends. Apart from other loot, he drops the Silver Hilt.
In-game description
| “ | This is a piece of Silver Sword, a vorpal two-handed sword used by the Githyanki and considered holy by them. It is magically sharp and can sever limbs and heads with ease. If the whole weapon could be found, it could be magically reforged. | ” |