Has the atmosphere of a 50's film

One of many cult Sci Fi flicks produced in the 70's that has the throwback feel of an old b movie from the 50's, SSSSSSS holds up well due to its makeup effects that despite being far from a Rick Baker masterpiece service the picture accordingly.

I wonder if the screenwriter for this flick took some cues from The Fly in how the David character gradually morphs into a reptile.