OK gang, I've looked at a ton of dimes tonight (still gong through the coin jar...time to cash in!) and found a 1987 with the mint mark (P) over the third number in the date. All other dimes I've seen tonight (hundreds?) have the mint mark over the last number of the date. Thoughts?
Prior to circa 1990 mintmarks were punched into the working dies by hand so the exact location of mintmarks could vary.