Check this one out... 4-string minstrel banjo! The frame is from 1865, but no idea when the photo is from.
I blew it up and counted five strings - I think the other peg is just off the picture.
I'm seeing 4 long strings and a short string as well.
I believe you guys... I don't think my screen resolution is enough to make it out though!
Definitely 5 strings. These new 27" retina iMacs are great!
Looks like 5 to me as well. Great photo.