Today I received an email that I couldn't expect at all. Enjoy !

I enjoyed your hackaday posting of the 2n554 flip-flop circuit.  I built the computer described in that  Popular Electronics article in high-school in 1964.  Those circuits were later reused in my KB/67 (Kalin-Burkhart) project.
Here's a bit more about the history of that flip-flop circuit. I was always curious where that circuit design originated, and did some follow-up.  That flip-flop was also featured in the January 1960 issue (page 65) of Electronics Illustrated in an article by Ronald Benrey.  He contributed many projects to electronics magazines during that time.  His homemade satellite appeared in the October 1958 issue of Popular Electronics.

Looks like the flip-flop circuit is from Performance Tested Transistor Circuits, (page 47) published by Sylvania in 1958.  Although that circuit uses a different transistor, 2n307, Benrey substituted the 2n554,  which was a common substitution.

Before finding the Sylvania document, I thought perhaps that the circuit may have come from a Motorola publication.There was a 2n554 application bulletin published, which I've not been able to find.  But I did find an ad (attached) for that bulletin.  At least from that write-up, the flip-flop circuit is not included.

(7% distorsion, yay !)

That demo computer described in the PE article also made the cover of Computers and Automation in Nov 1960.
Very brief description on page 20. One of these units was listed on ebay last year, 2 photos attached.

How awesome is that ?