Kujako- I do have a CPU 'skate' that I had a Mac Pro on for 4 yrs. I don't know what the metal is but after 4 yrs use it doesn't flex so is sturdy.
I received the skate 4 yrs ago as a gift; it has no identification on it (manufacturer or source), giver not around so can't ask for info. Needs a bit of cleaning but not hard & can do.
It looks a lot like the pics of the Japanese one but not as shiny, wheels smaller.
The base ht is ~3 1/4", wheels are nylon & ~1" diameter, length of inside bed=17.5", width=8".
Wheels don't lock, only go forward & back, not side to side.
If you're interested I'll take pics -1st ones didn't turn out, need better lighting, also not sure how to get in in here but will try if you are interested and I can get instructions for getting a pic on this site. Embarrassingly non-techy at the moment.
The Mac Pro went south--something elect. & I've given up, not worth my effort to do more. Have a new iMac.
So I'm willing to UPS the skate if you're interested in it. Feel free to say No. Just would like to find a good home for a Useful Object.