Anyhow, this February 1985 edition has a letter to the editor:
Italics in original.
So, we have an article from 1985 talking about the word “maxin’” and a possible source of prison slang dating back to the early 70s. The people on the other board claiming the word doesn’t exist are ignorant. They were known enough in 1985 to get a mainstream publication to write about it as “new slang.”