Interesting piece of postal history: a May 19, 1936 letter mailed from the Clift Hotel in San Francisco to Geneva, Switzerland with a franking totaling $1.38.  I’ve identified the stamps as Scott nos. 640 (8-cent Grant), 700 (30-cent Bison), and 571 ($1.00 Lincoln Memorial).  As you can see from the photos, someone (possibly the recipient) has written the Zeppelin transit info on the envelope.

Inside is a tattered and folded page from the New York Times dated May 3, 1936 with an advertisement for the Hindenburg.  On the back is a list of then-current Broadway shows.

Geneva “Telegraphe” receiving datestamp on the back.