All safety catches are checkered in some way or another to help provide grip . Ease of use and reliability in use are a prerequisite for this small but important part of a gun. The movement backwards is usually automatic upon opening the gun, so  the design must facilitate this sliding catch being pushed forward.
The Westley Richards design is one of uniqueness in that there is a good length behind the button which together with the two widely spaced lugs below make for a smooth and precise action. The large high button at the front  provides a larger than average area for grip and its height allows the thumb additional purchase when pushing forwards.
A significant difference is in the treatment of the button. My own nickname for  this is the  'Westley woodlouse'  ( pillbug or  rolypoly in the US ) . Instead of cross hatched checkering, all the sharp grooves are cut at right angles to the direction of travel,  giving the appearance of this attractive  well known small creature.
These are not just decorative lines, but are deep enough to do a real job under all circumstances. They give maximum grip under the thumb and ensure easy operation with a sweaty thumb or when wearing heavy gloves. It may not be the end of the world when a less than efficient safety catch design means the loss of a bird, but faced with a very large angry beast at close quarters the story could be very different.
