My ticket featured a 1914 photo of two cable cars stopped at a famous San Francisco intersection with an overlying headline naming the cable car lines. Three small photos illustrating how the cable car system works were placed under the main photo, along with the attribution "San Francisco Cable Car Collectors' Series." So there's a series of cards, which serves as an incentive to ride the cable cars to collect them all.

I noticed a detachable stub and, when turning the ticket over, saw that the flip side was designed to serve as a postcard.

So, after my ticket stub was torn off, I read the educational content which enriched my ride. Later, I jotted down a few highlights from our trip, stamped the card and sent it off to my Dad, who loved it and propped it up on his kitchen counter.

I obviously responded very positively to the piece, as did my Dad. He didn't want to give up the card when I asked for it back so I could write about it.

Not only did the ticket serve a dual function as an ticket and an educational "brochure," it provided cable car riders with an opportunity to become collectors and provided them with a natural viral marketing opportunity (sending the postcard to friends or family).

Absolutely brilliant and very low cost. No fee for distribution, media relations or postage. Just modest design and printing costs.