MILK TRAIN
A train that delivers and receives goods at every depot along the tracks.
Notice this train has 3 freight cars in front of 4 baggage cars. Then the passenger cars
trail behind.    The most important goods are on the baggage cars, the U.S. Mail.
Mail can also be delivered by just throwing it off a regular train as it passes, maybe at 20 miles per hour.   Picking it up was accomplished by mounting the mail pouch to a bracket extended from a pole and a metal arm extending from the baggage car would grab the mail pouch.

......................................................................................................From: Post Card Museum
Goto: Grand Rapids