Check marks usually indicate a user has some kind of NIP-05 which is just a technical term used that some web site reports that your user matches their backend.

The #OG is a nostr:nprofile1qqs9xtvrphl7p8qnua0gk9zusft33lqjkqqr7cwkr6g8wusu0lle8jcpp3mhxue69uhkyunz9e5k7qg4waehxw309ajkgetw9ehx7um5wghxcctwvsqs6amnwvaz7tmwdaejumr0ds2g5zx8 badge based on their Primal subscription.