It's a nice coin, but I think there are issues with physical crypto coins in general. The only way I could possibly make $ off of this coin is if the price of Bitcoin were to decrease significantly, I sell it (at basically a loss), collect say my 25 BTC, then the price of Bitcoin increases beyond the rate at which I bought this coin. On the flip side, if the price of Bitcoin increases immensely, then I've just lost out on the price increase of the 10 extra BTC I sent you, plus no one will buy it now for 20BTC because of the higher value of BTC. That is probably why you can't sell it for 20BTC.
It could go either way. It's hard to see how it could maintain such a premium if BTC was in the multiple thousands, but these coins are an icon in its history and there are very few.
On the flipside, if BTC dwindles to irrelevance it'll still be a gargantuan footnote in history and there still aren't any more of these coins.
The Zimbabwean 100 trillion dollar note had a face value somewhere around 20c near the end. They go for $10-20 all day long because of their historical value.