I recall that cel on YJ, but it went way higher 
than I thought it was worth, and it's even worse 
now.  The fact that none of the usual DP fanatics 
in Japan bid on it is particularly telling. 

Without a reference source, it's tough to say 
whether this is a legitimate hanken, production 
cel, or clever fan cel.

One thing that leads me to believe this might be 
a hanken is the lack of those big loopy black 
marker numbers that have shown up on the top of 
every Dirty Pair cel and matching background set 
that's come up for sale lately.  If you've bought 
any or seen any for sale (and there has been a 
massive flood of them), you're bound to know what 
I'm talking about.  

On the other hand, I'm fairly sure this is from 
the "Project Eden" movie, and most of the cels in 
the DP flood have been from the TV series.  If 
you have the movie handy, you might want to go 
through it again and see if this turns up as a 
cel.