This is an outdated and unique Japanese culture called "Inkan".
It is common practice to stamp this seal on documents and other items as proof of identification and approval.
As of 2021, there are finally more and more cases in Japan where "Inkan" are no longer needed for various contracts, so these seals will disappear with the times.
So, these are valuable NFTs.
Written on each "Inkan" is a famous Japanese surname.
There is only one NFT per surname.
Are there any Japanese surnames that you know?

Crypto Inkan

collection

CollectionAnalyticsPageQuery

CollectionPageContainer_data

isSensitiveContent

name

description

slug

owner

isCategory

bannerImageUrl

logo

verificationStatus

dropv2

metadata

statsV2

createdDate

totalCreatorFeeBasisPoints

defaultChain

isCollectionOffersEnabled

collectionOffers

numOpenCriteriaOffers

totalCriteriaOfferVolume

relayId

representativeAsset

assetContracts

discordUrl

externalUrl

instagramUsername

mediumUsername

telegramUrl

twitterUsername

connectedInstagramUsername

connectedTwitterUsername

redeemableCampaign

isTraitOffersEnabled

nativePaymentAsset

inspiredBy

enabledRarities

isVerified

campaignAnnouncementModal

campaignId

title

overrideUrl

ctaText

ctaUrl

playbackId

thumbnailUrl

query CollectionAnalyticsPageQuery(
  $collection: CollectionSlug!
) {
  ...CollectionPageContainer_data_2YoIWt
}

fragment AccountLinkV2_account on AccountType {
  address
  config
  isCompromised
  user {
    publicUsername
    id
  }
  displayName
  ...ProfileImage_data
  ...wallet_accountKey
  ...accounts_url
}

fragment BaseCollectionHeroBanner_data on CollectionType {
  name
  verificationStatus
  owner {
    ...AccountLinkV2_account
    id
  }
  dropv2 {
    __typename
    stages {
      __typename
      endTime
      ...useDropStages
      ...StageStartCountdown_stage
      id
    }
    id
  }
  ...CollectionHeroInfo_data
  ...CollectionHeroStats_data
  ...CollectionBannerActionBar_data
  ...useDropState_data
  ...collection_url
}

fragment CampaignAnnouncementModal_data on Query {
  campaignAnnouncementModal {
    campaignId
    title
    description
    overrideUrl
    ctaText
    ctaUrl
    playbackId
    thumbnailUrl
    id
  }
}

fragment CollectionBannerActionBar_data on CollectionType {
  relayId
  slug
  representativeAsset {
    assetContract {
      openseaVersion
      id
    }
    id
  }
  assetContracts(first: 2) {
    edges {
      node {
        blockExplorerLink
        chainData {
          blockExplorer {
            name
            identifier
          }
        }
        id
      }
    }
  }
  discordUrl
  externalUrl
  instagramUsername
  mediumUsername
  telegramUrl
  twitterUsername
  connectedInstagramUsername
  connectedTwitterUsername
  ...collection_url
  ...CollectionWatchlistButton_data
}

fragment CollectionDescriptionMetadata_data on CollectionType {
  ...collection_url
  metadata {
    custom {
      isMockDrop
      hideProgressBar
    }
  }
  statsV2 {
    hasFungibles
    totalSupply
    totalQuantity
  }
  ...useDropState_data
  dropv2 {
    __typename
    ... on Drop721LimitedEditionType {
      totalItemCount
    }
    ... on Drop1155LimitedEditionType {
      totalItemCount
    }
    mintedItemCount
    id
  }
  category {
    slug
  }
  createdDate
  totalCreatorFeeBasisPoints
  defaultChain {
    displayName
    identifier
  }
}

fragment CollectionFooter_collection on CollectionType {
  isCollectionOffersEnabled
  isTraitOffersEnabled
  slug
  defaultChain {
    isTradingEnabled
  }
}

fragment CollectionHeroBannerV2_data on CollectionType {
  name
  description
  bannerImageUrl
  logo
  ...BaseCollectionHeroBanner_data
  metadata {
    hero {
      desktopHeroMedia {
        __typename
        ... on ImageMediaType {
          mediaType
          imageUrl
        }
        ... on VideoMediaType {
          mediaType
          videoUrl
          thumbnailUrl
        }
        ... on MuxVideoMediaType {
          mediaType
          thumbnailUrl
          playbackId
        }
      }
      mobileHeroMedia {
        __typename
        ... on ImageMediaType {
          mediaType
          imageUrl
        }
        ... on VideoMediaType {
          mediaType
          videoUrl
          thumbnailUrl
        }
        ... on MuxVideoMediaType {
          mediaType
          thumbnailUrl
          playbackId
        }
      }
    }
  }
}

fragment CollectionHeroInfo_data on CollectionType {
  description
  ...CollectionDescriptionMetadata_data
}

fragment CollectionHeroStats_data on CollectionType {
  slug
  ...CollectionStatsInner_data
}

fragment CollectionInspiredBy_data on CollectionType {
  inspiredBy(first: 2) {
    edges {
      node {
        slug
        name
        ...collection_url
        id
      }
    }
  }
}

fragment CollectionPageContainer_data_2YoIWt on Query {
  collection(collection: $collection) {
    isSensitiveContent
    ...CollectionPageHead_collection
    ...CollectionPageLayout_collection
    ...useIsRarityEnabled_collection
    ...useIsOffersTabEnabled_collection
    ...CollectionTrackingContext_collection
    id
  }
  ...CampaignAnnouncementModal_data
}

fragment CollectionPageHead_collection on CollectionType {
  name
  description
  slug
  owner {
    address
    displayName
    id
  }
  ...collection_url
}

fragment CollectionPageLayout_collection on CollectionType {
  slug
  ...CollectionHeroBannerV2_data
  ...CollectionTabs_collection
  ...CollectionFooter_collection
  ...SweepContextProvider_collection
  ...useIsCollectionFooterEnabled_collection
  ...CollectionInspiredBy_data
}

fragment CollectionStatsInner_data on CollectionType {
  isCollectionOffersEnabled
  description
  slug
  name
  metadata {
    custom {
      isMockDrop
    }
  }
  dropv2 {
    __typename
    landingPageReady
    id
  }
  ...collection_url
  ...collection_poll_stats
  ...collection_live_stats
  ...collection_live_listing_stats
}

fragment CollectionTabs_collection on CollectionType {
  ...useIsAnalyticsTabEnabled_collection
  ...useIsOffersTabEnabled_collection
  ...useIsOverviewTabEnabled_collection
}

fragment CollectionTrackingContext_collection on CollectionType {
  relayId
  slug
  isVerified
  isCollectionOffersEnabled
  defaultChain {
    identifier
  }
}

fragment CollectionWatchlistButton_data on CollectionType {
  relayId
}

fragment ProfileImage_data on AccountType {
  imageUrl
}

fragment StageStartCountdown_stage on DropStageV2Type {
  __isDropStageV2Type: __typename
  startTime
}

fragment SweepContextProvider_collection on CollectionType {
  nativePaymentAsset {
    symbol
    id
  }
}

fragment accounts_url on AccountType {
  address
  user {
    publicUsername
    id
  }
}

fragment collection_live_listing_stats on CollectionType {
  statsV2 {
    floorPrice {
      unit
      eth
      symbol
      usd
    }
  }
}

fragment collection_live_stats on CollectionType {
  statsV2 {
    numOwners
    totalSupply
    totalQuantity
    totalVolume {
      unit
      symbol
    }
  }
  numOpenCriteriaOffers
  totalCriteriaOfferVolume {
    unit
    symbol
  }
}

fragment collection_poll_stats on CollectionType {
  statsV2 {
    totalListed
  }
  collectionOffers(first: 1) {
    edges {
      node {
        perUnitPriceType {
          unit
          symbol
        }
        id
      }
    }
  }
}

fragment collection_url on CollectionType {
  slug
  isCategory
}

fragment useDropStages on DropStageV2Type {
  __isDropStageV2Type: __typename
  startTime
  endTime
}

fragment useDropState_data on CollectionType {
  statsV2 {
    totalSupply
  }
  dropv2 {
    __typename
    stages {
      __typename
      startTime
      endTime
      id
    }
    mintedItemCount
    ... on Drop721LimitedEditionType {
      totalItemCount
    }
    ... on Drop1155LimitedEditionType {
      totalItemCount
    }
    id
  }
}

fragment useIsAnalyticsTabEnabled_collection on CollectionType {
  defaultChain {
    identifier
  }
  statsV2 {
    totalQuantity
  }
}

fragment useIsCollectionFooterEnabled_collection on CollectionType {
  defaultChain {
    identifier
  }
}

fragment useIsOffersTabEnabled_collection on CollectionType {
  isCollectionOffersEnabled
  defaultChain {
    identifier
  }
}

fragment useIsOverviewTabEnabled_collection on CollectionType {
  ...useDropState_data
  redeemableCampaign {
    __typename
    id
  }
  metadata {
    overview {
      modules {
        __typename
      }
    }
  }
}

fragment useIsRarityEnabled_collection on CollectionType {
  slug
  enabledRarities
}

fragment wallet_accountKey on AccountType {
  address
}
