I've been a collector for many years. Had a friend at church approach me this morning and said he found a 1916 Mercury dime in change received from a purchase. Does it have D mint mark I asked? he said no, it has a W. I said bring it to me next Sunday and I'll put my loop on it. Assuming he's correct, why would someone put a W on a 1916 Mercury?
All mercury dimes are like this. The W is just designers initials. The actual mintmark is on the reverse, not the observe.
The W is the initial of the designer - Adolph Weinman. It is actually an A superimposed over a W. The same thing is on the Walking Liberty Half Dollar. It may be infused (I don't remember off-hand).
1916-(P) Dime - minted in Phildelphia, no mint mark. Obverse (designer's initials between "Y in "LIBERTY" and date) Reverse (no mint mark) 1916-D Dime - minted in Denver, "D" mint mark. Obverse (designer's initials between "Y in "LIBERTY" and date) Reverse (mint mark "D" just to the right of "E" in "ONE") 1916-S Dime - minted in San Francisco, "S" mint mark. Obverse (designer's initials between "Y in "LIBERTY" and date) Reverse (mint mark "S" just to the right of "E" in "ONE")
The "W" is actually the designer's last initial. The mintmark is on the reverse to the bottom left of the fasces.
Not to be rude or picky, but the word is incuse. The designer's initials are raised on the Mercury Dime.