1913 postcard: "You can put it in a frame and hang it up"

In March 1913, Ruth mailed this postcard from Mystic, Connecticut, to Miss Myra Berger in Waynesboro, Pennsylvania.

Here is the note written in cursive on the back:

Dear Myra: I forgot to send the proof of Mabels picture but will do so the next time I write. Don't you think I am some artist? I did this picture that is the coloring. I think it is fun. You can put it in a frame and hang it up. I think they are cute that way. Love Ruth.

The sentence "I did this picture that is the coloring." — that's the exact punctuation and capitalization — confuses me slightly. I'm not sure whether Ruth is saying that she's the one pictured or if she simply colored in a photograph of someone else. (Obviously, Myra would not have needed clarity.)

I am curious about how this postcard was printed, since it appears (though I could be wrong) to be a one-off and not something that was mass produced. I assume it's a variation or refinement of the early practice of hand coloring postcard photographs.

Other than the freckle-sized and illegible logo on the front (shown at right, with the contrast and saturation increased), there is no publisher or manufacturer indicated anywhere on the card. So some elements of this postcard remain a bit of a mystery.

Do you reckon Sotheby's would be interested? Should I put it in a frame and hang it up?