If this KO closer was used on any NEMA 1 enclosure, I would say that it is in compliance.
NEMA's definition of a NEMA 1 enclosure states "Type 1 - Enclosures constructed for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment and to provide a degree of protection against falling dirt."
Since the KO closer in question will provide the same protection as the enclosure, the fact that it is thinner is a non-issue, regardless of the wording of the NEC. As thin as this closer is, i don't think I could poke my finger through it.
I've seen just about everyone on these boards, at one time or another, state that they would accept work that did not meet the letter of the NEC, I think this is one of those areas.
[This message has been edited by Tom (edited 08-07-2001).]
Few things are harder to put up with than the annoyance of a good example.