The items that can be categorized as an 'artefact' are the Gold Armlet, mid-14th Century, SIA Kebaya (Traditional Costume), 1968, Singapore, 'Coinafon', Public Telephone, 1970s, Singapore, and Malay coin, 1800s. These items are considered artefacts because they are objects that were created or used by humans in the past and hold historical, cultural, or artistic significance.