That is probably correct, I don't have any way of evaluating their collectible value as a time series. My response was half serious and half joke, when people discover large caches of currency, someone often pipes up "Gee but if they had put it into the stock market ..." which over long enough times is often (as in this case) no better than simply the intrinsic collectible value of the currency. Of course some currency has no "value" at all, I've got some East German Marks for example which you certainly can't take to your local currency exchange booth and get local currency for them. But I did have an offer from a coin collector which was more than their face value in equivalent Euros.

For the same reason I think a gold coin makes an excellent college graduation gift. For me it embodies the essence of the value of a college degree, on the one hand it has a 'face value', on the other it has a 'value in trade', and on the third hand it has value as an industrial ingredient in various products. It really captures the economic notion of value versus cost. And I see a college degree in the same way.

And the final bit, there was a comedian who once joked that as a kid they put all their money in a savings account to save for the future, but now realized that if they had just kept their toys in good shape I could have resold them in their golden years for a fortune!