Reporting from the official website ravencoin.org, Ravencoin is a peer-to-peer blockchain, handling the efficient creation and transfer of assets from one party to another.
Ravencoin is a protocol based on a Bitcoin code fork that adds features that are specifically, focused on enabling tokens to be issued on the Ravencoin blockchain.
These tokens can have any property the owner decides – so they can be limited in number, named, and issued as securities or as collectibles.
According to Ravencoin.org, you can create your own security token in minutes and trade it worldwide.
But you haven't given him the answer he wants. All you did was just getting him generic information written on their website
There are a few I know, but they are more about NFTs and seem not so popular. I personally haven't used the platforms so this is not an endorsement
1.
https://www.ravenist.com2.
https://rvnft.art/nft-marketplace3.
https://mellori.market/