As I plough through the old negatives, I sometimes find a photo with an old leather camera case in the shot. It's the same one, popping up again and again. So I asked my brother about it. Turns out it was our grand father's (Arch Stephenson) and he left it in shot sometimes. Our theory is he did it to stir up our father (Bill Stephenson) who would have thought it terribly unprofessional. Arch was the landscape photographer and Bill the portrait man and somewhat of a perfectionist.
So it seems this was a little inside joke between father and son. It puts a smile on my face, I hope it does for you too.