Silver signet ring, despite its name, isn't a means of entry, nor does it accord any special privilege. You can get it from Angus during Chapter III.
Source[]
- This same ring can be found on various Salamandra bodies.
- It can be found on the corpse outside the swamp cave in Chapter III.
- It can be found in a crate in the Crypt in the sewers during Finders Keepers.
- It can be found in a wardrobe in the House of the Queen of the Night in Chapter III.