Ha! Turn the clock all the way back to October 1974, my Dad photographed a soon-to-be birthday or Christmas present: Cool!
Found it! My Excel sheet had it listed as no photo, box unspecified (I also enter whether or not it has its own box). But it was in its original box! Here she is: You can use that as a template for repairing yours.
Since it's Athearn, you probably could cannibalize another Athearn single-dome tank car with an intact upper platform and other parts (train show finds are a great source of cheap organ donor cars). A new ladder could be fashioned from extra parts from industrial structure kits. A little straightening of the grab rail and it should look reasonable. All that is very easy to do. And fun!
Just the right amount of "fertilizer" around the bottom. Unlike this train show find : The only thing missing is the smell...