Defiantly not potatorum!
I'm rather familiar with that species.
I've got a variegated form and a plain blue form of potatorum.
They are more of a ball shape, producing numerous short wide leaves, with a very short tapered point to the leaf and a much more fine terminal spine.
My plant has certainly not experienced too little sun in the time I've had it!
It roasts in full sun all day, up until 2 weeks ago, when I drug it in, the color on the fresh growth in the 3rd pic is a little yellow tho...
