Unlikely. China's narrow gauge is mostly 30" (or is it 750 or 760mm?), not metre.I wonder if maybe those steamers came from China?
Having diesels in the 60s doesn't mean they didn't also have steam. I learned recently that there is no more "real" steam in Vietnam, but there was until about 2002.They were running deisel in Vietnam when I was there in the mid 60's.
Black smoke is usually an indication that things are not running as efficiently as they could be, although there are other causes too. One really impressive way to make smoke is to sand the flues... I've seen this done by a Shay at Ottawa's Museum of Science & Technology, and you'd swear that the thing was about to explode...is there a way to make our new steamer run black smoke like they did back then.