Ron Guth:
The 1898 Quarter Eagle is a common coin in the sense that there is an adequate supply to satisfy most collector demand. Of the dates in the 1890s, the 1898 is in the middle of the pack -- not as common as the 1897, but nowhere near as scarce as the 1892 and 1894. However, compared to the mega-populations of the dates in the early 1900s, this date is far less common.
MS67 examples make up a high percentage of the PCGS Condition Census, indicating the overall quality of this date and the attention paid to it by collectors.