Rereading this, a bell rang when I read the word "dissident". When Bush Jr. went into Iraq, he did so without the support of NATO allies or seeking UN support. As a result, the only country that went along was the UK. The prime minister in those days was Tony Blair, who was sharply criticised by the conservative opposition. They popularised their stance by calling Blair an "American lap dog". That episode would fit the counterstamp.
Peter
I'm not sure the Fitzwilliam thought this was actually a dissident coin although it was part of a huge collection they acquired that could be labeled that way. The collection was bought from Gavin Scott and numbered about 400 pieces. His reason for amassing the collection was to preserve examples of this type of coin from many different countries. I was fortunate to get a copy of their inventory, but only dealing with the Irish / British issues related to the Troubles...about 75 in total.
As I examined the sheets it became apparent to me that at least a dozen had no relation to the Troubles and likely weren't even of a dissident nature. Another dozen perhaps I couldn't make a determination on because I needed images to examine closely. To this day, I don't think they've been photographed so that's a dead end.
In any case, your explanation may be correct, but might it better represent something related to monetary policy?
Bruce