One of the most interesting non stamp stamps is a label that was printed at Britain's Jubilee International Stamp Exhibition of 1912. The design was the winner in a contest to find the image that would represent the British show, being unique, but not too far from the designs currently appearing on U.K. postage stamps. The contest was to find the "Ideal Stamp." They may have found the ideal label, but not the ideal stamp: The Post Office did not adopt the design for use on mail.
There is a category of stamps - actually labels - that are known as cinderellas. These, although they appear on cover with legitimate stamps are actually ephemera disguised as stamps. The collector of covers can barely avoid them, as they appear on many covers. Some of them, including French aviation vignettes merit their own catalogs filled with items that can be quite pricey, especially when used properly on aviation event covers.
In general, early event covers legitimize these labels and carry on a synergistic relationship with them, turning them into postal history and legitimizing them. Unused examples, after all, are unofficial and have no intrinsic value, as government issued stamps do and interest in them is only engendered by a single event.
Miscellaneous Ephemera; Philatelic Newsletters
But there are more esoteric bits of ephemera and they are found among collections and exhibits of postal history. Documents, letter heads, bills of lading, receipts are all good items to add to a collection, especially if they have ornate features and fancy engravings.
The collector of philatelic ephemera can also hit paydirt with old bank checks and drafts, which years ago were taxed, and happily the tax was paid with revenue stamps that were applied to the front or the back. There is also revenue stamped paper -- tax on the document prepaid. And although the art of the designs of revenue stamped paper are interesting, such items may be somewhat far afield for a collector of stamps, whether revenue or postal.
Newsletters of an earlier day are naturals for ephemera collectors. The right newsletter, paired with a stamp can explain the stamps purpose, including why it was issued, how collectors felt about it, as well as providing a context through philatelic journalism of the time.
Advertisements of the day give a good impression of what people's concerns were. Of course the early versions of what would become the most influential publications in the philatelic world - from Stanley Gibbons, Scott's, etc. - attest to the great changes in the hobby over the years and the success of certain companies as small eight page newsletters grew into hundred page slick publications.
Cards, Philatelic and Postal
One of the most interesting combos, which has everything for the philatelic ephemera collector is the postal Jubilee cards and envelopes issued by Great Britain for the 50th anniversary of the issuance of the Penny Black stamp - the world's first postage stamp as we know them - and the institution of uniform penny postage. The one cent envelope is covered with symbols of mail delivery (carriage, train, postman), while the card within features a portrait of Rowland Hill, father of penny postage.
The most ubiquitous piece of philatelic ephemera is the postcard. When they carry meaningful stamps and cancels - as do government postal cards from expos (Pan Am, Columbian, etc.) they are raised into the world of postal history. But mint post cards issued for these events earlier days, are ephemera without the philatelic connection supplied by the act of traveling through the mails. Nevertheless, government issued postal cards for these events have a place in a stamp collection when the collection includes ephemera.
Straddling the definitions of philatelic and ephemeral are stamp show cards. These cards, very similar in size to the jumbo postcards that were popular in an earlier day are issued by stamp clubs, dealer groups and the USPS and the government. Invariably picturing stamps that relate to the theme of the show - a reprint of the Pan American series for a transportation related theme, for example - they are more souvenirs than legitimate postal history, although a show cancels can push them toward the latter category.