An interesting group of original photography acquired by us from the estate of an engineer active with GM / Cadillac in the 1950's.

These appear to document some sort of road test based out of the GM Laboratory / Proving Grounds in Phoenix involving three different examples of historic Cadillacs, a 1915 ; 1935 ; and 1950?

There is some notation but not a ton and nothing that gives us a precise indication of the nature of the testing or a specific date.

I can make out 1951 on one of the Michigan license plates and a handful of names:

I've scoured my available print reference books and the internet and can't find any reference to whatever it is they are doing here, but it seems official and includes three GM factory-owned examples of iconic Cadillacs. 

There are 54 photographs (approximately 5" x 3 1/2" snapshots) accompanied by 45 of their original negatives. 

I've included many images here and will happily provide more upon request. Thanks for looking and please don't hesitate with questions.