1917 Mercury Dime MMs T16/T17

I believe, but am not sure, that the bottom "D" and the bottom "s" are the T16.

Type 1916 and Type 1917. The mint changed the puncheons and the hubs at the beginning of 1917. So roughly 20 percent of all 1917 Coins are supposed to be of the T16 variety.

No, there were several (minor) design changes. It's analogous to type 1 and 2 Buffalo nickels, though the changes are less dramatic. 1916 dimes had higher relief and several minor differences in the details in the hair, feathers, etc. Also, 1916 dimes, type 1 Standing Liberty quarters and 1916 Walking Liberty half dollars had textured fields, which was the preferred style of medalists at the time. For dimes, this has been called the "type of 1916".

Part way through 1917, they made a new master obverse and reverse master hubs to get rid of the textured fields (some big-wigs at the mint didn't like it), lower the relief and make some minor changes to the design. They changed the style of the mint-marks at the same time. A minority of the dimes minted in 1917 used the 1916 style. Between 1917 and 1918 they made some more minor changes to the obverse hub (but no further changes to the reverse), and that type was used through the rest of the series.

The higher relief in the type of 1916 is a factor in grading worn out 1916-D dimes because the wear pattern is much different than for later dates.

Thanks for the pictures, jmkendall (I was the person who originally asked). The mint-marks are pretty distinctive, so I think I can pick out the two types for '17-D and '17-S pretty easily, but the Philadelphia ones are trickier. I have a couple 1917-P that I think are different types, but it's hard to tell because they're in different states of wear.

I mentioned in another thread how I thought it was odd that the 1945-S micro-s variety got so much attention and dedicated slots in albums, but there were other mint-mark varieties in the series that are just as interesting but don't get any attention.

The difference on the obverse between the type of 1916 and the rest of the series is most noticeable on well worn coins. Here's a comparison of a 1916-D and a 1921-D in F-12.



The 1916 has a lot less detail in the hair and feathers toward the front of the wing. It's not just because they're being generous to the key date - it's the higher relief. Notice how the 1916 has much more detail toward the tips of the wings because they curve back behind the head more.

There are several details that are subtly different, like the shapes of the feathers, positions of various bits of hair, subtle differences in the profile and the shape of the back of the head, etc.

(Here's a reference that discusses the changes.)