Bill, this is way outside of my area of collecting but this site shows why it was just a one year issue and differed from the previous years, and also has some photos.
When I mention the 'Ugly' Head 1696, I am referring to what the excellent Dowle and Finn Irish reference refers to as the Type 2. (Please see the D & F page at www.littlemistakes.com/1696_Dowle-Finn_1696.jpg )
As you see, the Type 1 pictures William III in a normal way. But where did anyone get the grotesque image shown on the Type 2?
Bill
P.S.- I have other references and pictures, but never have seen a hint on the reason for the odd-looking obverse.