Stamps (Philately)/Envelope


Stamped Envelope
Stamped Envelope  
I'm not very knowledgeable about stamped envelopes/wrappers and would appreciate some info on the following. I have what appears to be an unused stamped envelope with a typical 3 printed imprint that looks like U436. It is printed/embossed on the inside of the envelope which is colored purple (except for the head) also inside the envelope. The stamp can be seen from the outside. I have attached a scan to help identify. Is this a common item or something unique? My thanks in advance.


Printing on the inside of the envelope is uncommon.  There is a market for error stamps such as yours, but it is highly speculative.  In general, the more dramatic the error, the more an EFO (error, freak and oddity) collector is willing to pay to get it.

I recommend you contact at least two U.S. error stamp dealers for an opinion:

Steve Crippe at

Jack Nalbandian at

Good luck!

-Mark Leon

I deal in United States Stamps
American Art Glass
and Halloween Costumes!

Stamps (Philately)

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Mark Leon


I am a collector of United States postage stamps, and also a stamp dealer. I`m a member of the American Philatelic Society (APS). My principle area of interest and expertise is in United States Stamps.


I've been selling stamps on the internet since early 1996. I maintain a stamp web page that concentrates on mint US stamps issued generally between 1890 and 2009. I'm an active seller on since 1996, under the user id "mleon". You can find my web page at

I have a Bachelor of Science degree in computer science from the University of Nevada at Las Vegas, 1984.

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