For a complete overview of Frank Perret's achievements, here is a link to Tom Gidwitz's website here
In his website, Tom Gidwitz present a picture of an envelope sent by Perret to Alessandro Malladra. The envelope from Tom Gidwitz's website here
As Tom Gidwitz explains on his website (I quote): "Perret sent this letter in late June 1919 to volcanologist Alessandro Malladra, Director of the Vesuvius Volcano Observatory from 1927 to 1935. Evidently the envelope contained photographs that Perret had taken on June 2 at Stromboli, where an eruption on May 22 showered 60-ton boulders on the island's village of Ginostra, killing four people."
On his website, Tom Gidwitz shows only the envelope but not the photographs that the envelope originally contained when Frank Perret sent it.
By coincidence, I recently received these postcards in my mail. Well, I must admit not really a coincidence: being an old book and volcano lover, I recently bought a used book written by Frank Perret and found the postcards in it. So here they are, written by Perret's hand:
Postcard 1 (front) :