s.d. lee is probably the photographer or at least the owner of the studio the picture was taken in. before cameras were a household item, people would go to pose for photographs in a studio. you would go sit for a photo with some kind of prop that was popular in those days, i.e. civil war soldiers often posed with sabres and other acoutrements of war. that bike is most likely a prop in the photographer's studio.

when you were done sitting for the photo, the photographer would develop it and mount it in a little cardstock frame like that to keep it safe. i'm a history major and i've seen a lot of old photos like this one. my grandmother actually has one much like this hanging in her living room, i'll see if i can get a picture of it and maybe some information about it when i see her next.