To answer the question right away: I don't know. Some may find it interesting, others may laugh at the idea but before we get into that let's first see what these crypto stamps exactly are:

"Österreichische Post (Austria) issued the world's first blockchain stamp on 11 June 2019...For the first time, a seemingly traditional product - the postage stamp - manages to harness the highly complex technology of the blockchain...The Crypto stamp is a physical postage stamp that has a “digital twin” in the blockchain....The NFC chip on the stamp can be read with any NFC-enabled smartphone. By scanning the NFC chip, you can check that your Crypto stamp has not been activated yet."

Ahh NFC meets NFT. OK, so they can be used as actual stamps and have a so called "twin" which you can also hodl as an NFT on the blockchain. There were already several regular editions and now this year also the first gold edition of these stamps has been issued which comes with an actual 1 gram gold bar. So with this gold edition, it seems that after Austria now also the Netherlands is jumping aboard the crypto-stamp train. A bit ironic considering how much they tried to hinder and control cryptos. Guess someone aka Dutch Royal Post PostNL smells money.😉

"The NL crypto stamp is a stamp that consists of 2 parts: a physical stamp and a linked ‘digital twin’. It is the Netherlands’ first crypto stamp. And thanks to our collaboration with Austrian Post, this is also the first crypto stamp issued by two postal services together!"

So there you have it, stamps. Regular and some kind of "gold edition" stamps that come not only with a physical stamp and an NFT, but also with a 1 gram gold bar (spot value about 55 Euros, stamp value about 95 cents) which they sell for 500 Euros. They have a limited supply of 499 (Austria version) and 999 (Netherlands version) of the gold edition stamps. The Austrian gold edition was already sold out long ago which might tell you something about it's demand, but then again it only had 499 pieces. So I guess time will tell if people really start to collect these as regular stamps or if the NFT value holds up.The regular versions btw had 60.000 stamps per issue and there have been four issues so far. I wasn't able to find any data on whether or not they have all been sold out as well.

Either way I hope you understand what this all means. At what point in the crypto-journey are we now exactly? At the point where we have governments censoring and trying to destroy the independent, privacy and decentralized aspects of crypto and at the same time roll out government issued NFTs which they somehow mashed together with gold and stamps.🙃

So now the grand conclusion: Should you invest in the gold edition of these stamps since they have a very limited supply? Someone is already re-selling the Austrian version for more than double the initial price online. The only sound and 100% guaranteed advice I can give you is this: Be sure to take the 1 gram gold bar off before you use the stamp and send out a letter.