Dan's explaination is bang on. There were 2 different fonts used for the 9's in 1899 ... a delicate one that is thin in the "hook" next to the knob, and a thicker one as well. Sometimes the delicate one is called the "small 9" ... the last digit, as Dan and others have explained, was handpunched so there are spacing and alignment differences as well. They were used interchangably and are combined in different marriages with one another. There are also 3 nice repunched last 9's (delicate), sometimes in tandam with with a R/P'd first 9 (evident on the inside right of the loop and the knob. The last 9 is always the one most offset. You will also find the 8 slightly R/P'd