There are a few ways to know if your hanken is the real thing.
One, you buy it straight from the studio.  Two, you buy
it from a dealer, which is most often the case.  The best
advice one can get in a situation like this is to trust your
source.  There are no markings on hanken cels to identify
them as such, no certificates of authenticity (which don't
mean much anyone as those are easily fabricated - just take
a look at that huge bust the FBI did a few months ago in
San Diego with all the fake autograph memorabila.  It
all had certificates of authenticity.....).  Hanken cels
usually start around $600 and go well over 10K for prime
ones.  If someone is offering you one for $200 I'd be 
suspect.

With eva cels selling for between $500-$3000 (and more)
I would expect a good hanken to be quite a bit of
$$$$.  Just my 2 cents.