To be honest, I never claimed to know what a "true" gyro is, but I would bet on the meat sliced and piled on a skewer, roasted vertically. But the kronos product I mentioned earlier is found on vertical roasters all over chicagoland,(and the country, per their info) and has been for over 30 years.as I also supposed before, the texture of it, when carved off the spit, seems kind of like a strip of meat(well....sorta). I dug deeper, and found that the kronos folks have or had a restaurant where they did the stacked slice method....old school style. But the price point was higher.
But the cones are the prevelent way because they guarantee best price while maintaining consistent product. Difficult if not impossible with stacked, sliced meat