This shot of a southbound Seaboard System (former L&N) coal train coming through Bee Rock Tunnel (47 feet, 7 inches...) on May 22, 1985 had a little reflected light off one of the internal elements of my Vivitar 35-150mm zoom (a common problem in a head-on shot of a train, looking into the headlight). This is called "ghosting," and it relegated this shot to the "dud" box. But, with some careful Photoshop cloning, it's now gone.
This slide was particularly important to resurrect because trains stopped running on this route in 1986-87. It was ultimately abandoned, and today it's an unfinished hiking trail. Because of that, any shot I took at Bee Rock is a "keeper" now.