Bottom line: You’ll see that on the 1918-D Mercury Dime, there’s a small mint mark D after the “ONE” in “ONE DIME.” Otherwise, the 1918-D Mercury Dime is almost identical to the 1916-D ...

(Today, these dimes are referred to as Mercury Dimes ... and Philadelphia (no mint mark), coins made in San Francisco remained the same. More than 600,000 dimes were produced in Philadelphia ...