Plastibel was introduced around 1965. So if born before that, your circumcision wasn't plastibel.
Gomco has the image of leaving the dark ring, but this is not always the case and other methods can also leave it. It is to do with your skin/pigmentation behaviour.
You have a good amount of inner foreksin left. But even baby technique can give that. Had you had small amount of inner foreksin left, one could rule out mogen style.