Sentimental cornerstone: 52' Mantle that was my 'diamond' engagement present from my wife.Personal collecting cornerstone: 58' Topps Aaron missing yellow ink was my first understanding of what feelings a vintage card could inspire....it also created the false impression i could 'outsmart' other collectors! The card that would probably most impress other collectors and be presumed to be my cornerstone card: 1919 W514 Joe JacksonCard that impresses me most, taking 4 hard years of searching ebay daily and international auctions regularly to acquire: 1964 Macrobertson's Cassius Clay