object/nightwatch/2 matches the site

public static HumanMadeObject NightWatch_2_Accession()
{
    var nightWatch = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/nightwatch/2")
        .WithLabel("Night Watch by Rembrandt");

    var accessionNumber = new Identifier("SK-C-5").AsAccessionNumber();
    var name = new Name("The Night Watch").AsPrimaryName();

    nightWatch.IdentifiedBy = [accessionNumber, name];

    return nightWatch;
}

• Role shortcuts AsPrimaryName, AsAccessionNumber and AsSystemAssignedNumber each add a single classification, with the AAT terms Primary Name, Accession Number and System Number.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/nightwatch/2",
    Label = "Night Watch by Rembrandt",
    IdentifiedBy =
    [
        new Identifier("SK-C-5")
        {
            ClassifiedAs = [Aat.AccessionNumber],
        },
        new Name("The Night Watch")
        {
            ClassifiedAs = [Aat.PrimaryName],
        },
    ],
};

Generated from the object the example builds: every property that is set, as object initialisers, with the vocabulary constants where a term is in the registry. The fluent helpers are a convenience, not a requirement; this form and the one as written produce the same JSON.