The Silver submachine gun is shinier than a normal submachine gun, and also has darker colored wood for the pistol grip and stock. Other than that, it is no different from the normal gun. It has no special stats, properties, or access to any different weapon mods. Weapon mods also get the same color as the original parts.
This weapon cannot be renamed at a workbench, because The Silver submachine gun does not have a unique item ID. The ID 1b28f7 is simply a leveled list the game uses to reward players with the Silver submachine gun during the quest The Silver Shroud. This particular idiosyncrasy is shared by only two other weapons - Ashmaker and the Survivor's Special.
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