This has been copied and pasted several times...I'm not sure who wrote it. One nice thing about this type of exchange is that the postcards are protected in the envelope and not damaged in the mail.

IN-Envelope Exchange
Send one New, Unused, Un-written on, Lighthouse postcard to each person on the exchange list. This exchange by being IN-Envelope allows the sender to add extras if they want to (not required). Some examples of extras that have been added in the past are: Extra postcards of the same lighthouse from different views, write ups or flyers of information about the lighthouse on the postcard, pictures that the sender has taken of the lighthouse on the postcard, Lighthouse Bookmarks, Lighthouse Calendars, or just any little extra that the sender wants to share.