fistfulladirt said:1971-D DDO
1972 DDO
1972-D DDO
1972-D (NO FG)
1973-D DDO
1974-D DDO
1977-D DDO
1982 (NO FG)
1987 P,D
S-PROOF CLADS

Check the 82. There are some out there with no "FG" (designers initials) on reverse. Can be $10-$20 from what I have seen on eBay.
You need to have a loupe to check the no FG. I have looked at plenty that look as if it is missing but under a 16x loupe, I can see it. I only have 1 that shows no sign under the magnification.
MU
This is correct. I believe a lot of the ones found by posters on here aren't true no FG. Wayyyy too many being found. There has to be no sign of the initials.