When Did Shuster Meet Kirby?

Here's a relatively well-known picture of Joe Simon and Jack Kirby...

The piece of art on the drawing table -- the splash page debuting the Boy Commandos from Detective Comics #64 -- suggests this photo was taken in 1942. Both men went into the service in 1943.

But I bring this photo up today not to try to date it. Check out the back wall, just above Kirby's head. That's clearly a drawing of Superman. Although it's a little too out of focus to really see any details, the basic pose is very reminiscent of how Shuster drew the character posing, and the "S" emblem on his chest is in a simple triangle, not the more familiar shield shape that became close-to-standard about a year before this photo was taken. This image looks like a mirror image of the cover from Superman #6.

So was this a sketch of Superman that Shuster himself did a year or two prior to this photo? Was this done by either Simon or Kirby to see how close they could come to replicating the style of the insanely popular comic? It seems to me, too, that the drawing is done directly on the wall -- I don't see any edges of a piece of paper. Did Shuster visit the Simon & Kirby studio at some point and doodle that on the wall? Or maybe one of the other Superman artists -- Paul Cassidy or Fred Ray perhaps? Although that seems unlikely since they were all-but-ghosting for Shuster at that point -- that doesn't strike me as something they'd "celebrate" by drawing someone else's character in someone else's style on someone else's wall. It was actually Ray who changed the "S" trinagle to a shield shape, and he mostly only did Superman covers anyway. And Cassidy was working remotely out of Milwaukee. But there was still a number of artists who professionally worked on Superman at that point, including several on the newspaper strip alone.

I'd be curious if anyone has done any more investigating about that particular Superman drawing. Was it actually drawn by Shuster? If so, what was he doing in the Simon & Kirby studio? Comic artists were a relatively insular community, but I don't recall ever reading about Shuster actually meeting with any other artists in the 1940s that didn't wind up drawing Superman with/for him. And if it was Simon or Kirby, why draw someone else's character while they were trying to bust their butts to invent new ones? And why put someone else's character on directly on their studio wall? I have lots of questions here that I've looked for answers to off and on for a few years without coming up with anything. Do any of you have any ideas?

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