The new N4's have an unfinished alder, not paduak body.
The Custom ones have the 'N4' sticker on too. The N2s have a swamp ash body.
I only know this regarding the newer reissue models though...so I fully stand to be corrected by someone knowing more than me!
At the end of the day, if you like the guitar, get it! I like the N-Series Washburns myself...