Agreed with @numist + composition changes. 1859: Indian Head Cent Starts 1866: Shield Nickel implemented 1883: Liberty Nickel 1892: Barber Coinage 1909: Lincoln Cent 1913: Buffalo Nickel 1916: Changeover to Merc, SLQ, Walker 1932: Washington Quarter 1938: Jefferson Nickel 1942-1945: Wartime coinage 1946: Jefferson Nickel 1948: Franklin Half 1959: Memorial Cent 1964: Silver replaced by clad Nice idea!
Yup, design change. I have always been fascinated with the way people used to live (and what they carried in their pockets. I used to work in my fathers store as a kid and gave out change to customers, I guess that isw where it came from.
1915-1916 though... the half changed in 1915 but the Barber dime and quarter went into 1916. Maybe that's too picky. (I think we can ignore the 1913 Liberty nickels).
I didn't state that very well. My point was that you could have two different sets for 1916 since the dime and quarter overlap.