I'm pretty familiar with Gentile '75 forward, and except for '76, they pretty much all the glass blower mark, and a few with the Gentile star, presumably for Star City.
In '76, I'm familiar with three special marks, all celebrating the US Bicentennial. The American Eagle (G on chest), the Liberty Bell, (again with a G in center), and the Tall Ships,(G on front sail).
I might be missing something though.
Here's a photo from a very good website showing a good number of American glass marks.
It says the Eagle was "1970's" and the Tall Ships was '77. I think that's wrong though. The Tall Ship procession was on July 4th 1976, sadly I remember it well, ships from over 30 nations took part. Perhaps it took Gentile time to create the mark, but I'd think it was only for '76.