Commemorative postal <a href="https://en.wikipedia.org/wiki/cover_(philately)" class="extiw" title="en:cover (philately)">covers</a> for the first run and millionth mile of the <i><a href="https://en.wikipedia.org/wiki/Pioneer_Zephyr" class="extiw" title="en:Pioneer Zephyr">Pioneer Zephyr</a></i>.  These covers were carried aboard the train on November 11, 1934 (first run) and December 29 <a href="https://en.wikipedia.org/wiki/1939" class="extiw" title="en:1939">1939</a> (millionth mile).  The graphic was applied by the <a href="https://en.wikipedia.org/wiki/Chicago,_Burlington_and_Quincy_Railroad" class="extiw" title="en:Chicago, Burlington and Quincy Railroad">Chicago, Burlington and Quincy Railroad</a> to commemorate the events.  The lower cover for the millionth mile commemoration also shows an example of a <a href="https://en.wikipedia.org/wiki/perfin" class="extiw" title="en:perfin">perfin</a> stamp, with the letters "CBQ", the <a href="https://en.wikipedia.org/wiki/reporting_mark" class="extiw" title="en:reporting mark">reporting mark</a> of the <a href="https://en.wikipedia.org/wiki/Chicago,_Burlington_and_Quincy_Railroad" class="extiw" title="en:Chicago, Burlington and Quincy Railroad">Chicago, Burlington and Quincy Railroad</a>, perforated into the stamp itself.
The graphics on the envelopes were created by the Chicago, Burlington and Quincy Railroad, a corporation that ceased to exist in 1970.
The commemorative covers were created in 1934 and 1939.  The scan of the covers was created in 2005.
This is a scan of the original artifacts in the collection of Sean Lamb (<a href="https://en.wikipedia.org/wiki/User:Slambo" class="extiw" title="en:User:Slambo">User:Slambo</a>)