Back Story
Right at the beginning of my smart home journey in 2016, I have been using MCO Z-Wave smart wall switches.

I have used a mix of both Series 3 and Series 4 MCO switches. All my 1-gang switches are Series 4 (MH-S411), and all my 2-gang and 3-gang switches are Series 3 (MH-S312 and MH-S314).

Sonoff T2UK - Box Front
Sonoff T2UK – Box Front