Interesting situation. I ran into the same situation with Fold Three. We know that Rosecrans used military photographers and only one was assigned to the Engineer Brigade, that being Bonsall. In newspaper articles from the Arkansas City Traveler it is stated that he was on secret service a great deal. Still it would seem he got a pay check and if so from whom? I want to thank you Mr. Martin for your help, there is much to this man that is most curious. I found his unmarked grave in Arkansas City, Kansas. A good number of his original photographs have gone for large sums of money in recent years and yet we know so very little about him. I can add though that he was a Quaker which makes his service even more curious.