They were turning to low-cost tool shops in Japan, Korea and China for the dies they use to stamp sheet metal into sculptured steel parts for automobiles.

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As well as the 11 stamps of the Doctor, there is a "miniature sheet" featuring a first class Tardis stamp and four second class monsters.

BBC: The extreme stamp collecting of first day covers

The result is a stamp of the posts that under a microscope looks like a sheet of bubble wrap, each covered with layers of electrolyte and the cobalt oxide anode.

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