Today arrived White Collar: Season 1 from the UK (5-039036-044622) which for some reason is not to be sold in Ireland.

It also claims to be a region 2 but NTSC box on the cover.

What program can I use to see if it's actually NTSC?

It happens more often than you think. A few UK Columbia/Sony releases are also NTSC like An Evening with Kevin Smith. Also, a few Eureka releases. I am yet to come across a PAL release from Eros International who distribute Bollywood movies in the UK.

I've seen it in music and special DVDs (like Kevin Smith), too. Most of the time they are region 0 and world-wide identical.

But I can't remember it seeing with a "standard" movie or TV series.

Yep; it's rare but not unheard of - as indicated by the replies here (add the first release of Sex and the City: Season 1 BTW).

I suspect it saves them a little bit in that they can distribute the same discs to R2 UK/Europe and R2 Japan who are NTSC... and the reason all R2 DVD players must have support for PAL and NTSC which makes multi-regioning them much easier than machines for (say) the US which normally only have the NTSC decoding parts in.