A postage meter (or franking device) is a machine for imprinting a legal substitute for adhesive postage stamps, either directly on an envelope or on a "meter strip" of paper designed to be imprinted and attached to the mail by the sender. 
The term "meter" refers, technically, to the device, while the term "meter stamp" refers to the impression. The term "meter slogan" is given by collectors to that portion to the left of a meter stamp which advertises a product or services offered by the postal meter user. Manufacturers call them postmark ads (advertisements). It could be said to correspond to the slogan portion of a slogan cancellation, except that its message is a commercial or public service one chosen by the user of the postage meter.
Meter slogan imprints may include only a message (slogan), only a graphic illustration, or both. Railroad companies have been frequent users of meter slogans on their mail.
Most U.S. collectors of meter stamp material refer to this interest,
however specific or specialized, as simply "meters."

Members of the Casey Jones Unit (and other collectors) who may possess
examples of appropriate railroad cancellations not shown on these pages may
assist in this ongoing project as follows:
1. Scan the item (at least at 150 dpi, preferred 300 dpi) and send the illustration to the webmaster, or
2. Send a high quality photocopy of the cancellation to Norman Wright the "The Dispatcher" editor by postal mail or in an e-mail .jpg file.
(Better copies of any cancels shown are also welcome)