I'm particularly interested in the memory carried by old postcard.
Most of these postcards were bought in some souvenir shop in a resort somewhere. I guess that people who appear on those old postcards do not notice they are being photographed. And one cannot guess where, how and when the postcard was taken.
And then, you can take various memories (the ones on those postcards) in your hand, over the years. Postcards give material existence to the memory.
I got this idea from the news after 2011 earthquake in Japan.
It reported that masses of photographs were found in crushed houses, which had been swept away by the tsunami. Postcards put memories of places and people, friends or family, on paper.