Cat.III is.... safety ...rated for 1000v, ...
and Ideal list a couple of their testers as UL 3111-1 compliant, BUT ....OSHA has apparently withdrawn that standard from their requirements !!!

......I dunno, I can't find the replacement standard

...and some trivia....the term "wiggy" is a trademarked Brand Name, and belongs to Sq D .
they originally sold the tester as the ....Wigginton.... and now the word has crept into the lexicon much like Xerox or Band-Aid.
I have mounds of useful info like this, don't we all?

Tom