A friend gifted me these 12 Indiana RPO covers shown below; I believe them to be identified as three #U311 and nine #U411b. All the #U411b appear to have a plate flaw as shown here
Question #1 - I assume that this is a plate flaw and that it is known?
All these covers appear to be 'return envelopes' from Ragon Brothers of Evansville Indiana. The Ragon Brothers were wholesale grocers and were established in 1888, it appears that they were also proprietors of the Diamond Coffee and Spice Mills. Here is an image of the Ragon Brothers building in Evansville CA late 1880s.
The RPO markings include the Danville & Cairo and Danville & St. Louis. I believe that these lines ran near Evansville as shown on this RR line map.
Question #2 – To John Becker… As the resident Indiana postal history guy, would these covers fit in your collection/library? If so, let me know and I'll pass them along to you.