PS. the defination of overstrike that I am thinking of is that, a new design is striked over an old design, i.e. not just double striking, but a complete new strike on a previous design.
An example could be found here:
http://img300.echo.cx/img300/8836/overstrikev27wm.swf
(Yes I did post this in the Russian coin forum too. Just in case someone here didn't notice it
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(offtrack story)
I just came across this as I have at least 5 overstriked coins or possibly seven, and there should be another 3 coming in @_@ Russia has too many of these...
I need to start selling these, or I will be an ultra poor man lol
But yea, I guess this started my interest in overstriked coins.
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Ok back to the story, well at least, I have seen some "official" French and Austrian coins that had similar features, and some other small nations that had such events too. Of course, there were some "unauthorized" overstriking, such as China's overstriking of their own design over Korea's 5fun coins.
I am assuming that the main reason for this is because the mints were either lazy to produce new planchets, or there was really a shortage of materials.
I guess there could be similar examples when the Spanish conquerers were bringing their silver coins abroard, as their coins were counterstamped, but I don't know much examples of overstriking...
Now, please enlight me with your knowledge...