It's 1955, and made up as pure vanity for a special event in Bedfordshire on 30th April that year. The company that makes them has a web site:
http://poplargreg.com/
I originally had them made for my miniature traction engine.
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There is a thread in the Malvern Arms section of TM on this also.

Better phot showing the tax disc in-situ, with Emily doing her 'Maggie Thatcher in a tank' impersonation.



Tim