This first-day cover from October 24, 1932, is pretty cool.
1. It features the 3¢ William Penn stamp, which commemorates Pennsylvania's 250th anniversary. It was one of six commemorative stamps issued by the U.S. Post Office in 1932. (The others were a 2¢ Olympic Winter Games Lake Placid ski jumper, a 2¢ stamp for Arbor Day, a 3¢ Summer Olympic Games runner, a 5¢ Summer Olympic Games discus thrower and a 3¢ Daniel Webster.)
2. It was postmarked at 1:30 a.m. on October 24, 1932, in Chester, Pennsylvania. I suspect many of these prepared covers were postmarked at 1:30 a.m. There's an eBay auction for one right now.
3. It features a cachet (stamp) for the Delaware County Chamber of Commerce. The cachet notes that William Penn first arrived in Chester on October 28, 1682. (The first commercial cachet was produced in 1923, and you can read more about their history in this article by Marjory J. Sente.)
4. This cover was mailed by Frederick M. Gittings of Catonsville, Maryland, (who had a nifty return-address label) to Miss Florence Jones, also of Catsonville.