Sculpted by: Tony Cipriano
Release: 2017
Edition: Limited
Used material(s): Cast in silver- and gold-plated white metal
One of: 600

Signed: Israel Skelton

First appearance: Small World (one-shot)
 Lets you enter the dollhouse, makes you tiny
 Dollhouse front door

More information:
(possible spoilers)

When the Small World Key is used on the dollhouse, it gives you an entry in it and you will become as tiny that you fit in the house.

Source: Locke & Key Wikia