I had the opportunity to have my Peruvian friend San Marco, one of the 250 pieces, my San Marco OxPro Prototype and Drass Prototype.
So I do the brief comparison under sunlight and this was the result as you can see in the video ( watch it on 720p or 1080p resolution ):
Left side : Drass - Prototype Chocolate Dial
Center : OxPro - Prototype 29 pieces - Very Black Dial
Right side : OxPro - Limited Edition of 250 - Black Dial