To answer some of my own questions.
NEMA TYPE 3R
Rainproof and Sleet- (Ice-) Resistant-Outdoor-Type 3R enclosures are intended for use outdoors to protect the enclosed equipment against rain and meet the requirements of Underwriters' Laboratories, Inc., Publication No. UL 508, applying to "Rainproof Enclosures." They are not dust-, snow-, nor sleet (ice-)proof. They shall have conduit hub or equivalent provision for watertight connection at the conduit enctrance when the conduit enters at a higher level than the lowest live part, provision for locking, and provision for drainage. When completely and properly installed, these enclosures shall prevent the entrance of rain at a level higher than the lowest live part.
PART II - ENCLOSURE CONSTRUCTION
(a) All holes cut by the panel manufacturer for conduit are below the live parts or conduit hubs as marked on the enclosure are used.
(b) No other openings are cut by the panel manufacturer unless the holes are closed with equipment marked for use with that type enclosure (see substitutions below) and installed in accordance with the instructions provided with the closing equipment.
Openings may be closed by Equipment Marked