send out a number of letters every month (and the number is starting to pick back up now that I have more people who send letters BACK) and I'm always interested in how the world was different when information and personal correspondence was well...personal.
Don't get me wrong - I love the convenience of the digital age, but it always seems hollow and cold when compared to a book (rather than an 'e-reader') or a letter (rather than a post on facebook or an email). So I am continually looking up little details about books and letters and found several groups on the net that are attempting to keep those old traditions alive.
One of the more interesting traditions that seems to have all but forgotten is the idea of marking your books. Ideally, a book that you owned my be lent out to another person and it was important to know from where they came so you could return them. Therefore you'd need some way to mark each of your books. Printers would make up personalized plates (small pieces of paper that were often glued into the end pages of a book) to help reflect the character of the owner and to denote the book as theirs. These were called 'Bookplates'.
A bookplate, also known as ex-librīs [Latin, "from the books of..."], is usually a small print or decorative label pasted into a book, often on the inside front cover, to indicate its owner. Simple typographical bookplates are termed "booklabels".
Bookplates typically bear a name, motto, device, coat-of-arms, crest, badge, or any motif that relates to the owner of the book, or is requested by him from the artist or designer. The name of the owner usually follows an inscription such as "from the books of . . . " or "from the library of . . . ", or in Latin, ex libris .... Bookplates are important evidence for the provenance of books.
This is an old practice but one that I think is very cool.
A letterplate, then, would be essentially the same concept as it would record from whom the letter was sent. Sort of like a stylized 'return address'. Rather than being an 'Ex Libris' it would be an 'Ex Calamus', meaning "From the Pen of..."
As you can see from the image I cobbled together - it's not that hard to put something like this into your letter writing habits. Conceptually you could have the letterplate printed on labels that are then affixed to the back of the envelope - or have the envelope printed with them via a home printer.
I've added some additional ideas for an "Ex Calamus" below to get some ideas rolling.
I have no idea if there are any examples out there since I can't find anything on Google's image search.