OP have you googled 1958 doubled die? You can see pics of actual ones in which you don't need a microscope to see the doubling, its visible to the naked eye like the 1955 DDO
Machine doubling. The '58 is very distinctive http://varietyvista.com/01a LC Doubled Dies Vol 1/DDO 1958.htm
PMan would say doubled die. Is it possible that a doubled die or variety has not been found yet? From my understanding there was many dies made to make millions of pennies
