Triton Aquatronic Ultra 2 switch
This is the second replacement cover assembly in about 2 years as the original and first replacement both suffered the same failure. The off/on dial develops a crack which allows the dial to spin on the spindle without operating the switch. The cracks are identical.
Should have bought another Ivory 2 as these have never failed.
Thank goodness Shower Doctor always have these replacements to me without delay.