Very well could be... that is a carbon steel slide, and in an area if worn concealed, could have been against owners sweaty side. A little light oil and 0000 steel wool will make it disappear most likely. Not a sufficient reason to turn it away, if gotten for the right price! Slides can be refinished easily, if desired... frames on the other hand are anodized and a lot trickier... people who are "ring bearers" can seriously scar the anodizing on the frame, as bad or worse than it taking a "skip" along some concrete!!