I found the Alfred E. Neuman Holy Grail ---
The first picture of Mad's maddest mascot!
This is a cropped photo of Ritter's Dental Parlor at Northwest Corner of Flatbush Avenue & Schermerhorn Street Downtown Brooklyn Circa 1905.
It comes from Brian Merlis & Lee A. Rosenweig's Photo Compendium
"Brooklyn Heights & Downtown Volume I 1860 to 1922"
The book was published in 2001
Buy the book if you want to see entire image!
EDIT: After poking around it seems i'm not the only one to find this
Was Alfred E. Neuman from Brooklyn?
"It Didn't Hurt a Bit" Kid: Mysteries of Melvin