Curious Set of Three Real Photo Postcards of (Jesse) James-Younger Gang Members

Curious. I found these three real photo postcards together, and believe they date to the 1940s or so, while featuring photos taken in the late 1870s I believe. Depicted are members of the notorious James-Younger gang, American outlaws lead by Jesse James and his brother Frank, active in that incarnation from the late 1860s until 1876, when the Younger brothers were captured in Minnesota during the unsuccessful attempt to rob the Northfield First National Bank. (Jesse James would later organized a new gang, active until his death in 1882.) I think these RPPCs must have been taken of (quite make shift) sort of historical society museum exhibition, or similar--maybe even just documenting loose pages in some sort of archive, or school report! I love the hand-written notes above and below the photos--posthumous photos of the bodies of gang members Clell Miller and Charlie Pitts along with mug shots of sorts of Cole and Bob Younger--including description of Charley [sic] as "from a good fami