This is the earliest known postcard in the SJU Archives collection.* It is made of leather, and is postmarked Collegeville, Minn., September 12, 1907. It measures 3 1/2 x 5 1/2 inches, and has an undivided back.
Even if it were not postmarked, a postcard aficionado could guess this postcard's approximate age by its material and layout. Leather postcards are considered novelties. Introduced in 1903, leather postcards were at their peak of popularity in 1906 and 1907, and could still be found as late as 1910.
This postcard has an undivided back. Note the inscription on the back, "This side for the address only." The United States did not allow messages on the back of postcards, only addresses, until partway through 1907.
* SJU Archives has an Italian postcard that may be earlier, not directly related to St. John's. And we have a souvenir letter that may be earlier than the leather postcard. Both are shown later in the exhibit.
For more information on leather postcards, see:
Howard, Sherry, "Short-lived frenzy over leather postcards," Auction Finds, 2016.