It contained the message, phone number and web address. Surprisingly nice results. Others I met did the same for an extended period of time including at Flea markets, parking lots at swap meets, etc. who put a unit in their cars and RVs and/or mounted the removable unit to their pickup truck roof with surprising positive results. Some had their units encased in weather-proof cabinets.
Note: Many jurisdictions don't allow you to drive with it running in the window, so find a good place to park.
Maybe check it out?