Carrier Stamps

Is anyone familiar with these?
This one is up for auction on ebay, pretty cheap.
What are they? I can't find them in my regular Scott's.
Kind of interesting. Is it worth pursuing?

Ok, I found this, with the help of the Arago website (Smithsonian).
Scotts: Official issues. Issued by the US Government to facilitate payment of fees for delivering and collecting letters.

But this is listed as an LO3, an 1875 reprint of the 1851 original. And Scotts only lists it as unused.
Being a reprint, should I be wary of the cancel? Possibly a forgery?

Thoughts anyone?

http://www.ebay.com/itm/Carriers-St...em4ab2a5b299

LO1, the issued carrier stamp, was part of the original set of 1851 issues. You can see that it is really a "combination" of the 1c and 3c stamps of that issue - Franklin and the color from the 1c, and the design and lattice work from the 3c. Note that it is non-denominated. The stamp was only issued in a few cities and is EXTREMELY rare. If this is LO3, it is a reprint issued well after the period of use and, by definition, would have a fake cancel.
They are listed in the Scott's catalog under Carriers and Locals. Look them up in the index to find the pages in whatever year you might have.