| The centre of the impact area may be indicated by a design within the boundary of a square whose sides are 0.375 inches (9.53mm) in length. Such a design must not unduly influence the movement of the ball. Decorative markings are permitted outside the impact area.
The reason for this Rule is to permit small, decorative logos in the centre of the face or at the side of the impact area. Decorative markings or logos that marginally encroach on the impact area, i.e. by less than 0.25 inches (6.35 mm), may be permitted. However, any such markings must not be designed to unduly influence, or have the effect of unduly influencing, the movement of the ball. Markings outside the impact area which are designed to influence the movement of the ball when it has been mis-hit would be contrary to this Rule.
Fig. 38 - Decorative Markings