I have not seen this type of error in a collection. If it exists, it is a treasure and I would be VERY interested in seeing it! Normally a collar will fail in a way that does not stay "contained" like this.
After this happened we did go to a larger format coining collar in order to avoid this happening regularly.
That's why I have hung on to this SO long. I just can't imagine parting with it just as a novelty. There is no faking this!- Timothy