The Swiss Railways Watch – based on the immortal Swiss railway clock – is the world’s most legible timepiece. The question facing Mondaine: how do you improve on perfection? The watchmaker has introduced numerous variations, including reversing the dial colors (white hands on a black dial) and adding complications (e.g., the Sports Day Date and Stop-2-Go). But it’s the Mondaine Ultra Thin that cracks the nut . . .