Thanks again Don:
I found a reference to the following NEMA information (been around for a while) in the NECH commentary under "Qualified Person":
http://www.nema.org/stds/hazards-hot.cfm#download Working on de energized equipment would be the best way whenever possible, and in the commentary for the NEC 110.16 rule a summary is given related to safe work practices in 70E.
I have seen new installation around the country where these warning labels are provided with the panelboards in a brown envelope. They are not usually adhered to the equipment.
I am often asked if this rule is retroactive and naturally I say no -- but recommend that they give some though to the liabilities and the possible fines that may be given by OSHA.