object/nightwatch/52 matches the site

public static HumanMadeObject NightWatch_Classified_With_Local_Concept()
{
    var nightwatch = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/nightwatch/52")
        .WithLabel("Night Watch by Rembrandt");

    nightwatch.ClassifiedAs = [
        new LinkedArtNet.Type()
            .WithId("https://linked.art/example/concept/painting")
            .WithLabel("Local Copy of Painting")
            .WithEquivalent(Aat.Term("300033618", "painting (visual art)"))
    ];

    return nightwatch;
}

• Terms outside the registry The vocabulary registry holds only the terms linked.art itself publishes, so a dataset's own concepts, places and people are written with Aat.Term, Tgn.Place and Ulan.Person, giving the id and the label.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/nightwatch/52",
    Label = "Night Watch by Rembrandt",
    ClassifiedAs =
    [
        new Type("https://linked.art/example/concept/painting", "Local Copy of Painting")
        {
            Equivalent = [Aat.Term("300033618", "painting (visual art)")],
        },
    ],
};

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.