Frog-themed digital collectible cards from the mid-2010s are getting retooled for fast sales in the white-hot NFT market.

This NFT thing is changing the game older people wanted paintings they could hold and touch and see. NFT want it to be digital and that makes all the difference in the world it can be shared and you will own it till you die or sell it. This is priceless as anything else we are having to give to our children, life is good. This is the real deal.

The newest craze in the hot market for non-fungible tokens (NFTs) maybe a vintage series built around the ubiquitous Pepe the Frog meme.

Known as “Rare Pepes,” the tokens were minted as digital collectible cards back in the mid-2010s by blockchain pioneers focused primarily on Bitcoin and traded using a niche platform known as Counterparty.

Encouraged by the increasingly eye-popping price tags for NFTs, some Rare Pepe collectors have begun using a years-old software protocol known as Emblem Vault to reconfigure the digital cards to run on the Ethereum blockchain. Then, they’re listing these “wrapped” Rare Pepes for sale on the dominant NFT marketplace OpenSea and turning smart profits.

Over the past few days, at least one Rare Pepe has changed hands for 149.99 ether (ETH), worth about $500,000 at current prices. Another copy sold for 111.1 ETH early Monday. Such price tags fall short of the million-dollar sales netted for some CryptoPunk and Bored Ape Yacht Club NFTs, but industry executives speculate the Rare Pepes could eventually reap even richer proceeds due to their historical significance.

“One of the things we have been witnessing is that the all-time highs for these Rare Pepes are doubling or tripling over the past couple weeks, specifically due to them having access to the capital on OpenSea and more broadly on the Ethereum blockchain,” Emblem Vault co-founder Shannon Code told CoinDesk in an interview.

The digital collectible card that sold for $500,000 was minted as one of 300 in September 2016, according to OpenSea. It bears a green-fleshed likeness of Dorian Satoshi Nakamoto, reported by Newsweek in 2014 to be the inventor of Bitcoin, though he denied it.