I've seen 2 different styles, one with dimples for the wing nut one without. I remember someone saying that the non-dimpled was a repop. I'm really questioning that after looking at the 2 personally. They are virtually identical with the exception of the dimples. Size, ridges, stamp marks, gasket and finish. One thing I've noticed that more with the HEI seem to be without dimples but not all. Possibly coincidence. Thoughts and Experience?