The era is early 21st century…(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif). Not to answer for Dennis but I believed he did answer the question when he said
“Since my railroad is mountainous and curvy and requires mostly short line type cars, I decided to build
some 20ft in 20.3 scale boxcars, I am not into precise scaled or trying to make an exact replica of true prototypes.”
I would be curious if at every there were any “normal” narrow gauge freight equipment that small. But my guess is that this is about the “feel” of a small narrow gauge and practical for making small curves and steep inclines.