I would like to thank Michael for helping me to post the pictures, and Nick for his excellent summary of the USS Shenandoah during the Civil War. Nick's conclusion that there is not necessarily a way (absent provenance) to know which Ship Shenandoah, CSS or USS this British Red Ensign was associated with. As I have subsequently learned, The 'British Red Ensign' would often be flown by foreign military or merchant ships in an honorary position when visiting British ports. The act of 'Flying False Colors' was also an accepted strategy in certain military circumstances, Providing the true colors were raised prior to actual engagement.
The truth is, I know almost nothing about Flags, and am very happy to have found this forum. Im sure that there is a way to approximately date the flag by looking at or testing the materials or weave. There was no suggestion on the part of the man I bought it from that the flag was from any USS or CSS Shenandoah. He reasoned that because it was a British flag it must have come from a British ship. It came from an attic in Northern Maine.
I welcome further questions, comments or suggestions. Thanks again, Charlie Sorrentino