.....was reading an oooooollllddd issue of Hop Up last night, had an article on some classical Hi-Po piston cofiguration (mosyly for Buicks). All the pictures they had, shared one similar trait, despite their different concaves and faces such. Each piston in the center of the face all exhibited what can only be described as something that looked like a pistol shell primer and plate embedded in the surface. Anybody explain what its purpose was? Got me kinda curious.
It seemed too purposedly there to be a machining mark, but could be. That is a good point, I didn't think of that.