I say 1916-D. If you look at a 1916
Lincoln Cent and then look at the angle and depth of the hit above the date, I can see where the "6" was altered to appear to be a "0".
If it were in fact a 1910-S, the alterations would double, because the "S" looks like a "D", the "S" does not appear to have taken a strike where it would have been altered to look like a "D".
So to go from a 1916-D to a 1910-D, takes one very precise hit to alter it.
To go from a 1910-S to a 1910-D I see no hit the "S" took to change it to "D". Plus if in deed it were a fairly Rare 1910-S It would have to overcome the rarity of the 1910-S, plus take a hit to the "S" to make it appear as a "D". I see no evidence of that.
So to go from a 1910-S to a 1910-D takes two steps, Rarity and precise hit.
To go from 1916-D to a 1910-D take only one precise hit to the 6 to achieve that.
In addition the 1910-D does not exist. So that compounds
the possibility from Rare to extremely rare.
Simplest solution is probably the correct one.
Dan