Author: Published by DownBeat magazine. Photographed by Charles B. Nadell (per this scan). Credits: *Original source: The photo was originally published in the December 1, 1939, issue of DownBeat magazine (Vol. 6, No. 14) alongside "Guitarmen, Wake Up and Pluck!", an article written by Christian. A scan of the original page can be seen at WorthPoint in low resolution, or a higher-res scan of an exact reprint can be seen via Twitter.
Instant source: Scan via PBS. Cropped (to match original dimensions as published in DownBeat) and retouched by uploader.