If am right I believe your 40 percent stacking is based on the weight of the silver coin you bought in correlation to the copper coin, and since the copper coin was free I think it is a fair bargain. I am following up with your coin stacking journey in other to see how far you will achieve on it
The coin is 40% silver and 60% copper. So although I only paid for each coin once, the price was based on the amount of silver in the coin, not the copper. So in essence, I got the copper for free, but they aren't separate coins.
I'm glad you're enjoying watching my journey!