Moonglo

I believe I am in possession of a Structo 20 die cast Cadillac. It appears to be an exact copy of every Structo 20 I have found with the exception of the missing “Structo” stamping under the roof. My model indicates 20 only. The only other anomaly is missing stamping protrusions extending from back window support toward trunk. Please see comparison to actual Structo 20 model. Could it possibly be a prototype? Any information you may share is appreciated.