I dug out my Stackmat timer, and found a 2032 lithium coin cell for it, too. Promising start - then I remembered it had a problem, the left side touchpad didn't work correctly, it was 'permanently touched', so the timer ran off the right pad only. Not useless, and pehaps ideal for OH use. But I thought I'd better fix it. That turned out ot be a major bit of brain surgery. Eventually I sorted it out. When I get time, I'll take a few pics and add some instuctions etc to a thread on this Forum: "Inside the Stackmat timer".
So for some fun with my refurbished gadget ... I thought I'd try and recreate these mad-sounding 0.5 second solves that Rami et al, do on the 2x2x2. Four moves? So I figured the 'sexy move' on a 3x3x3 would suffice. I surprised myself, managing to get below 1 second, a 0.92s came up, so I guess that sub-0.6 is not so crazy. If you're young, obviously.