B20なんてのも珍車の類でありましょう。

JNR B20 Class

This class was the smallest loco in JNR steam fleet then and missed most standard JNR practices. Actually this class was a JNR version of standardised war time industrial loco developed in WWII. They did not have enough equipment to haul trains and used only for switching in yards. Most of them were decommissioned not so long after WWII and only one or two survived when I took railway photos.