Read the responses from other collectors below as 
well.

But basically all I'm going to say that 
production cels from this sequence is pretty 
common.  My friend has one himself.

Also, when AIC creates official reproductions, 
they never use an image such as this (B cel; 
character's eyes are closed; not a key scene).  
Reproduction cels (even rip-offs) are almost 
always prime shots (key moments in the anime; 
full image with lots of detail).

The only thing that's a copy here is probably the 
background, but I think you already knew that.