A correction to my earlier post:
The New Haven Railroad began the practice of having a "zero" prefix on the road numbers of its electric locomotives in 1906, when it was building its AC electrification between Woodlawn, New York and Stamford, Connecticut. The zero indicated that the locomotive was "0ther" than steam. This numbering also applied to New Haven diesel locomotives beginning in 1931 and lasted until steam engines were retired from the railroad in the 1950s.
Thanks for the additional info, MELGAR... You're still a treasure trove