C38? Info Needed On A Small Revenue (I Think)

what is this (marked C38) that looks like a small silver 3 cent peice or "trime" as they was called in the mid 19Th century? This looks absolutely dead on for the obverse of one! almost like a rubbing or an actual inked coin in press? I saw this in a catalog someplace and it was really old reference material so that got my curiosity up. Does anyone know why these were used and a possible actual scan of one?
Thank you for indulging my curiosity friends! Keeps it interesting for me! I would love to end up with one of these if they are not super rare or expensive of course.

It's in the "Carrier's Stamp" section of the Scott Specialized Catalog of US Stamps. Referenced as image C38, it is actually catalogued as Scott 8LB3 issued in 1857. 2011 SCV was $22,500; on cover $55,000. It is said the used example off cover is unique; only four covers are known to exist.

For some examples, check out this 2002 Siegel Auction reference on "Rarities of the World" (#2403 and #2404) at this link:

http://www.siegelauctions.com/2002/846/y84656.htm

Oh my goodness! That's a costly little piece! Like I said I was looking through an old reference guide and seen it and because I am a coin collector it really stood out hence my curiosity. OK well I think the coin would be more obtainable to me than that. That is fascinating though. Thank you again wt1!