A scene midway through the movie reveals a sign on the side of Dean's tow truck that reads "McCoppin Scrap". The end credits offer us an alternate spelling: Dean McCoppen.
The story takes place in 1957, but in the junk yard scene where the giant is spinning Hogarth around through the air in a junk car, that car is a 1959 Caddilac.
In the scene while Hogarth is talking to the Giant in the clearing shortly after bumping into the branch, it shows the Giants head without the dent, shows Hogarth, then shows the Giants head again this time with the dent.
Are there other Iron Giants besides the one featured in the movie?
A
Yes, in a deleted story board scene hints that the Iron Giant isn't the only one of its kind. When the Giant starts to sleep, his "dream" is transmitted to Dean's TV which shows brief footage of other Iron Giants.