No its definitely not zinc rot I learned about that awhile ago its definitely a stamp or extra lettering inside the D in God. Almost like the D was stamped over another letter or number. But I cant figure it out lol. I saw one other person with the same thing on their 1983 D on the D in God but I cant find his thing now and he called it a DDO
error and I forget what he was selling it for. (doesn't matter what he was selling it for of it's not worth anything lol. Anyhow thanks for some information I'll keep searching for what it is.