In my opinion the model M&P and later the model 10 in it's various and sundry dash configurations is not the classic. It is the gun for the masses with millions and millions being made, making it the most common S&W out there. A great gun no doubt, but produced in too many numbers to be anything other than common place.
Saying a gun is a classic puts it in the class with the Colt SAA, the 1911, the pre-64 Winchester and the Winchester 94. The Luger, High Power and the flat top Blackhawks also come to mind. My idea of the classic S&W would be none other than the Registered Magnum and all the 357 offspring that followed in the line afterwards, up to and including the 27-2. Visually, none are more appealing than the shorter barrel models such as the 3 1/2, 4 and 5 inch guns.
There's a couple more that are worthy of honorable mention: The Triplelock, The 29, the 19 and the 57. I guess my opinion is the product of my experiences and the guns of my youth.
As a consulation, the entire line of S&W revolvers makes the brand "The Classic American Brand" in my humble opinion.