I have one of those lamps with a magnifing glass in the center and pretty much look at all coins older than 1990. The younger coins seem to be pressed differently and seem to wear out faster. I do mainly halves. Unless I hear of an error in those dates than I'll start looking closer at those. I look for double dies and sometimes even pull a machine double if its interesting. I check for missing ingraver initials, die cracks, planchet errors, or anything out of the ordinary. Might not be any value to some of them but it keeps this old retired guy busy.
See my post "oddities from my last box" about half way down the page.
I do, I have found 100 1974D double dies, 1 straight clipped planchet, several die cracks, 2 or 3 struck thru debris and several weak strikes (these are to the point that almost the complete date is missing but the rest of the coin is struck strong).