I've been collecting NYS license plates for 30+ years and all the information I've seen, says the "Veterns", D.A.V., etc, "vanity" type tags were introduced with the 1973-1986 series of plates. In other words, they didn't exist in 1957, to my knowledge.
Note: I should further assure everyone that I'm not being pejoritive to our Vets - the word "vanity" is used above as a descriptive word understood in the plate collecting hobby to describe any non-general issued plate and is not to be disrespectful in any manner whatsoever to our military Veterns - I'm one, too!