bobby131313 - I agree with you that the puncheons are entirely different. The Heritage C/S looks real while the
ebay C/S is wrong. The C/S has a hollow central area - it (the punch) should be convex not concave - therefore the central part of the stamp produced on the coin should be the strongest NOT the WEAKEST part of the punch. The only time I have seen central weakness on this c/s is when it is weakly set and the host coin had a depression at the point of contact. The depth of the counterstamp in this case, PRECLUDES such a central weakness in my opinion. Pure and simply the stamp itself is a FAKE.
I would also concentrate my efforts in making comparisons using the side with the world globe. Whoever created that side did a VERY POOR job. The lines of Latitude extend beyond the edge of the globe and they are irregular in width - THOSE LINES should be uniform in thickness not irregular like these. To that add the cross on top of the globe - WOW!
The host coin being a fake is absolutely a given only in part because of the ties of this seller (likesunshine2004) to the Beijing forgery group. 1807 is one of their known dies as is the obverse die from "Potosi". I have seen several different examples from this die pair and may in fact own one of these myself - only without the stamp.
My point was that this is the first FAKE Minas Gerais counterstamp that I had seen recently and it looked like the Chinese were moving into a new area of forgery. They have already counterfeited many other C/S's (England, Protugal and others). So care has to be exercised at all times when dealing with counterstamps. My concern is that many people will be fooled by the C/S and if it is applied to a real coin it will compound the difficulties.
TwoKopeiki - the resemblances between the two counterstamps are purely superficial. It is like a counterfeit
Trade dollar from China - it looks generally like the real thing until you start to look at the fine details and how it was made. In this case, the minor details do not match the original and the punch face seems to have been prepared incorrectly.
Sap - I find some of the comments on the other coin site rather unbelievable. I certainly hope that none of them is bidding on this coin.