Likely taken during an expansion or re-tooling period. It looks like fresh concrete on the conduit. Of course, they could have washed the entire shop floor with fullers earth or whitewashed it, but doubtful. Notice the Xs inside the circles on the equipment - like it was recently marked by an inspector verifying placement against floor plans?

One of the photos in the series shows a bunch of shells in the background, maybe that has something to do with it as well?

Joe, that's what was freaking me - the artillery shells standing next to a shop engine! What the ding-dong?

If I'm not mistaken, that shop engine or something very close to it is displayed at the Smithsonian American History Museum.