I've gotten a pair of minifigure legs new out of the box with no 'LEGO' logo on the underside of the top of the foot a while ago. I've purchased new pieces where only one leg is imprinted. And as of late, all legs have been imprinted. Same thing with headgear and helmets. Some have the LEGO logo, some don't. When did Lego start imprinting 'Lego' inside the toes on plain leg assemblies?