Looking closely, some of the none standard bits I can see;
Extra exhaust relief ports
Different tilt lock mechanism
Side shift gears, instead of the tillershift which I believe was standard on these 15's
Not sure what this is/was? On the clamp bracket.
Rubber plug, where the carb drain tap was? And two holes? I've seen an electrical plug fitted here on the D-Class 40, so maybe battery charging?