How Often Do Identical Die Varieties From 1815 Appear?

I had collected bust half dollars for a considerable period during the 1970s and found Overton's work with die varieties fascinating. I assembled well over 100 varieties (real and counterfeit).

After some time doing that I wondered if Mexican 8Rs could be identified in the same way.

I started with a few very common dates 1832-1836 Zs 8 reales coins. I quickly concluded that finding identical die varieties was much harder than I ever expected.

I examined many, many hundreds of coins and discovered there were many more different die types than identical dies. So I discussed my project with Dave O'Harrow author of Hooknecks. He indicated that my proposed project was nearly impossible. His reasoning was simple and therefore elegant as far as a scientific theory goes.

The Mexican 8 Reales were produced as bullion export coins and the majority of these exports were eventually melted. He postulated that dies were shorter lived than those of the US bust half dollars and that the survival rates were far lower. He also indicated it was generally well known that many entire die outputs (sometimes almost all production from one year) were shipped overseas as bullion.

So I did some comparisons based on mint outputs starting with Overton. I can recreate the thought process. Look at 1822 - Overton indicates a mintage of 1,559,000 coins which was created with 14 obverse and 14 reverse dies. There were actually 15 different die marriages used.

Some clear inferences can be drawn from the manufacture - first is that dollar coins need more striking force than half dollars. Although the silver in both cases is the same there is actually MORE pressure needed for a larger diameter strike - not 100% more but a significant amount.

Second most Bust Half dollars were retired and retained by banks after 1853 so the period of circulation of bust halves was short. This means survival rates for bust halves was high.

I came to believe that when you see more than one copy of the identical die type (in close proximity) you need to be extra cautious that you are not being fooled by multiple copies of numismatic forgeries. Many authenticators use the same technique to spot counterfeits - no news there.

So here is my observation. I noticed that in one cycle of ebay (10 days) that three 1815 Lima Peru 8Rs were posted. This is not typical. But when I looked at the dies I noticed that two were from the same dies.

Here are the two coins:

http://www.ebay.com/itm/331500300137

http://www.ebay.com/itm/EXCELLENT-H...371282686050

Does anyone else have comments? What do you think?