A good question - I don't recall seeing a clear diagram to categorically answer this. One of the parts list diagrams appears to show the piston recess at the top, but gives no clues for the damper valve.
From memory, my recollection is that the recessed edge of the piston is indeed at the top, and taper of damper valve at the bottom (in fact, I have a feeling that with the various circlips and snap ring in their correct places that it may only go together if as above).
I'm sure others will share their views, and hopefully confirm.
Cheers - Chris R.