Niobium Postage stamp cover
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Postage stamp cover.
People who collect stamps like to have "first day covers" which contain a sample of the stamp canceled in a fancy way. This one also contains a sort of reproduction of the stamp in, amazingly, niobium foil with colors created by careful oxidation. It's iridescently beautiful, though the niobium foil version of the stamp is not a legal-tender sort of stamp. Here is a picture of the whole package showing the real stamps next to the decorative niobium version:

Warut Roonguthai, who kindly provided this sample, sent the following information about it and the similar tantalum version he sent:
I believe that Royal Selangor (the company that produces FDCs (First Day Covers) for Malaysia) put metal cachets on FDCs because they are an expert in making metal objects/arts. So they want to show their ability to make those cachets.There are other versions of cachets like pewter and silver, but I don't think you are interested in such naive metals, and they can't be anodized to create colors. Royal Selangor started their business with pewter because there are a lot of tin deposits (in the form of cassiterite) in Malaysia and the southern part of Thailand.

The tantalum cachet I gave you is the only one they have produced! Now they only use niobium for making colorful cachets for FDCs since tantalum is much more expensive than niobium.

Best wishes,

Source: Warut Roonguthai
Contributor: Warut Roonguthai
Acquired: 16 August, 2004
Text Updated: 29 January, 2009
Price: Donated
Size: 1"
Purity: 99%