For calendar year 2005, there were sixty-four patents granted on putter related inventions. Of the sixty-four patents granted, thirty-seven of them were design patents, while twenty-seven were utility patents. However, this simple statistic does not tell the whole story.
Very few manufacturers would ever admit that a putter’s design is simply ornamental, or that it was designed merely to be aesthetically pleasing. According to most manufacturers, the design of their putters is attributable to a functional performance improvement that is only found in their product. Therefore I suspect that at least 50% of the putter designs that are protected by utility patents also have a corresponding design patent. The fundamentals of design patent protection are explained here.