Flat crystals have their place in the scheme of things, I suppose, but the one annoying thing is reflections - especially from nearby lamps. By comparison, a domed crystal makes a reflection smaller and, if the underside is equally curved, it's reflection is also smaller. For example, this Stocker & Yale model 490's flat glass crystal shows no mercy when it's under a desk lamp.
The standard flat crystal on this watch is 30mm diameter and 1.5mm thick. A 30mm, 2mm thick, "double domed" mineral glass crystal was purchased for $7, installed, and the result was excellent:
The two pictures were taken at the same distance and in the same position. The lamp distance was about a foot above the watch. The domed crystal has an unpolished chamfer on the top and the crystal projects about a 1/2 mm from the anodised aluminum flat-topped bezel:
The side view is much improved. The angularity of the bezel is relieved by the domes' curve, which itself complements the curved chamfers formed on the side of the plastic body.
Was thinking of selling this watch, but now it's keeper!!
Best regards, xpatUSA