Public API

{
  "dataset_version": "0.9",
  "object": {
    "id": "np-rmb-001",
    "accession": "NP-RMB-001",
    "title": "Self-Portrait in a Velvet Cap with Plume",
    "date": "1638",
    "medium": "Etching, possibly with drypoint"
  },
  "claim_count": 18
}

{
  "@context": "https://schema.org",
  "@type": "VisualArtwork",
  "name": "Self-Portrait in a Velvet Cap with Plume",
  "artMedium": "Etching, possibly with drypoint",
  "creator": {
    "@type": "Person",
    "name": "Rembrandt Harmenszoon van Rijn",
    "sameAs": [
      "http://vocab.getty.edu/ulan/500011051",
      "http://www.wikidata.org/entity/Q5598"
    ]
  }
}

The Wikidata item for the 1638 self-portrait identifies the work and the plate, not this sheet, so it is emitted as exampleOfWork and never as sameAs. Many impressions exist; they are different objects.

?state=

Normalised New Hollstein state — I, II, IV. Rows whose institution states no state are excluded rather than guessed at.

?holder=

museum · library · university · private · unlocated · art_market

?country=

Country of the current custodian, e.g. Netherlands.

{
  "type": "census",
  "count": 27,
  "records": [
    {
      "id": "CN-rijksmuseum-rp-p-1961-989",
      "institution": "Rijksmuseum",
      "city": "Amsterdam",
      "accession_number": "RP-P-1961-989",
      "state": "I",
      "source_url": "https://www.rijksmuseum.nl/en/collection/RP-P-1961-989"
    }
  ]
}

Filters combine with AND and are case-insensitive. Unknown parameters are ignored and named back to you in the response rather than treated as an error.

id,holder_type,institution,city,country,accession_number,state
CN-rijksmuseum-rp-p-1961-989,museum,Rijksmuseum,Amsterdam,Netherlands,RP-P-1961-989,I
CN-the-british-museum-1910-0212-376,museum,The British Museum,London,United Kingdom,1910-0212-376,II

{
  "type": "claims",
  "count": 18,
  "records": [
    {
      "id": "CL-ARTIST",
      "field": "Artist",
      "value": "Rembrandt Harmenszoon van Rijn (1606–1669)",
      "confidence": "probable",
      "evidence": [
        {
          "id": "EV-ACQ-INVOICE",
          "tier": "primary_document",
          "title": "Bonhams invoice and purchase documentation, New York, 2023"
        }
      ]
    }
  ]
}

{
  "type": "evidence",
  "count": 5,
  "records": [
    {
      "id": "EV-ACQ-INVOICE",
      "tier": "primary_document",
      "tier_rank": 2,
      "title": "Bonhams invoice and purchase documentation, New York, 2023",
      "access": "on_request",
      "cited_by": [
        "CL-ACQUISITION"
      ]
    }
  ]
}

{
  "type": "questions",
  "count": 12,
  "records": [
    {
      "id": "RQ-01",
      "slug": "does-this-impression-carry-the-signature",
      "title": "Does this impression carry the signature “Rembrandt f. 1638”, and if not, why not?",
      "status": "open",
      "difficulty": "low",
      "suitable_for_student": true
    }
  ]
}

{
  "type": "provenance",
  "gaps": 1,
  "records": [
    {
      "id": "PV-003",
      "type": "gap",
      "is_gap": true,
      "date_display": "1638 – 2023",
      "title": "No documented ownership",
      "confidence": "unknown"
    }
  ]
}

{
  "type": "bibliography",
  "verified": 3,
  "records": [
    {
      "id": "white-boon-1969",
      "type": "catalogue_raisonne",
      "authors": [
        "Christopher White",
        "Karel G. Boon"
      ],
      "title": "Rembrandt's Etchings: An Illustrated Critical Catalogue",
      "year": 1969,
      "verified": true
    }
  ]
}

@book{white-boon-1969,
  author       = {Christopher White and Karel G. Boon},
  title        = {{Rembrandt's Etchings: An Illustrated Critical Catalogue}},
  publisher    = {Van Gendt & Co.},
  address      = {Amsterdam},
  year         = {1969},
  note         = {Bibliographic details confirmed against a published record.}
}

{
  "type": "states",
  "catalogue": "New Hollstein (Hinterding & Rutgers, Rembrandt)",
  "count": 4,
  "divisions": 5,
  "records": [
    {
      "state": "I",
      "headline": "Before the jaw is strengthened",
      "documented": true
    }
  ]
}

{
  "type": "glossary",
  "count": 28,
  "records": [
    {
      "term": "Impression",
      "category": "technique"
    }
  ]
}

{
  "type": "changelog",
  "count": 5,
  "records": [
    {
      "id": "CH-001",
      "date": "2026-08-12",
      "type": "release",
      "summary": "Record published at version 0.9"
    }
  ]
}

{
  "@context": "https://schema.org",
  "@type": "Dataset",
  "dataset_version": "0.9",
  "dataset_date": "2026-08-12",
  "counts": {
    "claims": 18,
    "census": 27,
    "questions": 12,
    "comparators": 8
  }
}

?q=

The query. Required; an empty query returns the list of searchable types.

?type=

Optional filter: object · claim · evidence · census · question · provenance · bibliography · state · glossary · changelog · comparator · education · story · policy

{
  "query": "watermark",
  "count": 12,
  "results": [
    {
      "type": "question",
      "id": "RQ-04",
      "title": "Watermark identification",
      "href": "https://rembrandt.aidispatch.xyz/research/questions/watermark-identification",
      "snippet": "…transmitted-light capture would record any watermark fragment…"
    }
  ]
}

Two things to know if you validate it. The canvases carry behavior: ["placeholder"], which is not one of the registered Presentation 3.0 behavior values and will be flagged as unrecognised; it is an extension value, and the authoritative statement is in each canvas’s summary. And the canvas height/width are the recorded dimensions of the sheet in millimetres rather than pixels of a master image, since there is no master image; canvas dimensions are unitless and carry only the aspect ratio.

Ids are the comparator ids from the dataset, for example rijksmuseum-rp-p-1961-989.