On a trip over to Rockland, ME, I got pics of the Owls Head lighthouse, and went over to the Maine Eastern RR to see what was going on, if anything. It wasn't long until I found this: Morristown & Erie C424 4235, switching out the Dragon Cement transload facility on the coast. Here's one of the cars used in this traffic: It's a 100-ton whalebelly covered hopper used in bulk cement service. It's lettered for the cement plant.
Don't believe I've ever seen one of those cement cars in actual service. Just in photos. They must be in captive use? Boxcab E50
That's my guess, as the cement plant is several miles inland along the ME line. BTW- Maine Central is operated by the same folks who run the Morristown & Erie.