This shows that since 1947, the rate of return on investment of this coin has been constant. The one sale where the price dropped slightly does not change that fact. This graph could easily be extrapolated to the future to predict when the coin will sell for $10M or even $100M or $1B, but I will leave such speculation

Here are the details and formulas behind my graph. The rate of return formula is @Rate(end number, prior #,period of years). As you can see, it changes and varies. Here's what it shows from 1984-1991 and again from 1984 to 2010: as the average rate of return during t4he applicable period. The numbers matter and vary based on the formula. I did mine on Quattro Pro for Windows but it should also work on Excel.