>>9940937O is pretty close, depending on WHICH O scale we're talking about. British O is 1/43, Continental Europe is 1/45 a d US O is 1/48. "Heroic" 28mm is pretty close to 1/48. You could fudge it a bit and go with On30, that is O Scale narrow gauge that runs on HO track. The trains are smaller, which would go well with 28mm and there's a fair amount locomotives and rolling stock that, if not exactly period correct, are pretty close to what was running in the period. Pic related is an example.
