Hi Walt.
That's a S-1. It's a re-pop of the Aurora kit.
Monogram acquired some of the old Aurora molds in the late 80's (IIRC) and released some of them.
The Maserati 3500, Ferrari GTO and the Porsche 904 were in this series.
Monogram did some retooling on the Porsche . The others were released pretty much as Aurora had done them back in the early 60's.
I don't think the Ford GT 40 was re-released, and the Avanti is "god knows where" .