Optical-reflection type Augmented Reality (AR) mirror displays use half-silvered mirrors attached in front of a digital display to show virtual objects overlaid into the physical world reflected in the mirror. Prior works mostly displayed 2D images on the surface of the mirror hence suffered from visual depth mismatch between the optical reflection of the 3D physical space and the virtual image. In this paper, we propose to use 3D visualisation to overcome this problem and improve the user experience by providing better depth perception for watching and interacting with the content displayed on an AR mirror. As a proof-of-concept, we developed two prototype optical-reflection type 3D AR mirror displays, one using a multi-view autostereoscopic 3D display and another using a head tracked stereoscopic 3D display that supports hand gesture interaction. A preliminary user study showed that the participants were able to perform selection tasks faster and with less error under 3D visualisation, and felt the 3D visualisation required less mental effort, was more comfortable to watch and interact with compared to the traditional 2D visualisation. The results also indicated the participants felt the virtual image was closer to their body, supporting the visual perception model of 3D AR mirror we postulated.