Current American postage stamp.

[Vimto]

This is a difficult question to categorise so I will put it into this quiz section which I know receives widespread readership.
I often receive mail from The United States that bears a small stamp with "USA NONPROFIT ORG." printed on it. It depicts what appears to be the rolling ocean and some trees in blue and the sky in an orangey-red. The left-hand and right-hand side is perforated but the top and bottom edges not so. These stamps are invariably not franked (cancelled). For what purpose are they issued? Are they postage stamps? Have they any value? Are they maybe, a charity stamp? Please advise.

[DrFilth]

you can see a lot of the american stamps issued on here

https://shop.usps.com...000003&WT.ac=10000031

[DrFilth]

lots on google about these stamps

Search ResultsWhy doesn't the USPS cancel "nonprofit" stamps? - Straight Dope ...
boards.straightdope.com › ... › Main › General Questions - Cached5 posts - 4 authors - Last post: 2 Mar
Every time I receive something in the mail from a non-profit organization, it comes with an uncanceled "USA NONPROFIT ORG." stamp on it. ...
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►USA Nonprofit Org. 1995 USA Postage Stamp Unused | eBay
cgi.ebay.com › Stamps › United States › 1941-Now: Unused - CachedUSA Nonprofit Org. 1995 USA Postage Stamp Unused. Item condition: --. Price: US $10.99. Buy It NowBuy It NowBuy It Now. Add to Watch list. Start of panel ...
USA Nonprofit Org. 1998 USA Postage Stamp | eBay
cgi.ebay.com › Stamps › United States › 1941-Now: Unused - CachedUSA Nonprofit Org. 1998 USA Postage Stamp. Item condition: --. Price: US $10 ...
Show more results from ebay.comUSA Nonprofit Org. 1998 USA Postage Stamp
www.ioffer.com › ... › Stamps › United States › 1941-Now: Unused - Cached7 Dec 2009 – us stamp 3c iwo jima #929 mint vf/nh/og $8.00 ... USA Nonprofit Org. 1998. The stamp is in good condition, & measures 3/4" X 1". ...
eBay - USA POSTAGE $.02 STAMP US INTER.REV. on PHOTO, Similar ...
shop.ebay.ie/sis.html?_kw=USA+POSTAGE...STAMP
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- Cached50 items – Postage Due 4C Stamp Markings US Stamp on Canada PM. Location: USA ... USA Nonprofit Org 1996 Mnts USA Postage Stamp Unused. Location: USA ...
Archive of 2005 PNC Info.
www.pnc3.us/pnc3.org/Archives/archive_2005.ht
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- Cached12/20/05 - The (39¢) PSA Lady Liberty & U. S. Flag stamp from Ashton ...... seem sharper- especially the white writing on the stamp (USA NONPROFIT ORG.)" ...