DC Comics produced its own house fanzine in the early to mid 1970s.  The JSA appeared in a number of these issues.
 

No.8, September 1975 - The Carmine Infantino issue concludes with an outstanding little article by Anthony Tollin, "Badges, Buttons and Secret Codes, too... just 10c to cover postage and handling!" which looks at DC's golden age fan clubs , the Supermen of America, the All-American Flying Club - later American Observation Corps - and the Junior Justice Society of America. Whilst the back cover is a Supermen certificate, page 48 shows B&W images of the third type of Jr JSA certificate and the membership badge.  Ironically the certificate belonged to none other than Super- JSAfan Roy Thomas, then Editor-in-Chief at Marvel Comics!!   [This article is where I first encountered info on the Jr JSA]

No.14, March 1977 - Special Issue, All About the Justice League of America by guest writer Mark Gruenwald details the JSA in the guest section as well as reprinting some B&W cover images of JLA/JSA teamups. [Many of which I had never seen before].  Mark was the co-author with Dave Lofvers of the 1973 fan publication The Complete JLA Reader.

No.16, December 1977 - Golden Age Issue contains Paul Levitz's article on "Dating the All-Stars:  How old are the members of the Justice Society today? JSA writer Paul Levitz explains his criteria for dating each member in their current adventures."  There is also a Joe Staton and Bob Layton center spread of the JSA rescuing Wonder Woman from Hitler,  and  "A Small Meeting of the JSA: fan Fred Schneider details his work in building a complete set of models of the Justice Society."

The Amazing World of DC Comics Copyright © DC Comics Inc.

I purchased my copy of No.16 many, many years ago - I can't remember where, or when.  I just know it was a real treasure of my collection for the last 20 years as it was the first fanzine I bought.  The other issues I picked up on a trip to Sydney about 2 years ago.  Just fluked a good find!