Thank you to everyone who provided resources for me. I learned from someone off-forum that the engine is actually by a company called Adachi, who produced these as kits during the 1960's. I hope to detail and paint this locomotive to match D51 498, which still operates to this day. Fortunately for me, the detail changes between its as-built configuration and its excursion appearance are minimal, so this prototype allows duel-era usage (with some fudging of details, of course).