Pure speculation:
In restoring our Dauntless early-mid 70s we had excellent support from Douglas Long Beach, notably from the late-great Harry Gann. Also had some input from NavHistory office in DC. Researching markings beyond the modeling norm, I found nothing comparable to the photo.
Guesstimate: some plane handlers might have pushed on the aft portion of the fuselage where there was not much structure, leading to dimples/dents? Also, it was Death or Worse to push on control surfaces. Sort of the aviation equivalent of Ranching 101: SHUT THE DAMN GATE!