‘415s’ OR ‘0415s’?

Confused by the terms ‘415’ and ‘0415’? The class was originally designated ‘415’, but became ‘0415’ when it was placed on the ‘duplicate’ list. Locomotives gained a ‘0’ prefix to their numbers when placed on the duplicate list. For a full list of when they received ‘duplicate’ numbers, see www.semgonline.com/steam/0415class_data.html