object/nightwatch/9 matches the site

public static HumanMadeObject Nightwatch_9_Measurement_Assigned()
{
    var nightWatch = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/nightwatch/9")
        .WithLabel("Night Watch by Rembrandt")
        .WithClassifiedAs(Aat.Painting, Aat.TypeOfWork)
        .WithHeightDimension(379.5, MeasurementUnit.Centimeters);

    var attrAssignment = new AttributeAssignment()
        .WithLabel("Measurement of the Night Watch");
    attrAssignment.CarriedOutBy = [
        new Group()
            .WithId("https://linked.art/example/group/nightwatchteam")
            .WithLabel("Operation Night Watch Team")
    ];
    attrAssignment.PartOf = [
        new Activity()
            .WithId("https://linked.art/example/event/operationnightwatch")
            .WithLabel("Operation Night Watch")
    ];

    nightWatch.Dimension![0].AssignedBy = [attrAssignment];

    return nightWatch;
}

• Metatype classification The second argument classifies the first, not the object: WithClassifiedAs(Aat.Description, Aat.Statement) says this is a Description, and Description is a kind of Statement. The Plain C# form shows the nesting.
• Dimensions and physical description Each helper builds a Dimension with its AAT type, value and unit, or a classification with its metatype: height, width, colour, shape, page count, component count, file size, duration in days.

var humanMadeObject = new HumanMadeObject
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/object/nightwatch/9",
    Label = "Night Watch by Rembrandt",
    Dimension =
    [
        new Dimension
        {
            Value = 379.5,
            Unit = Aat.Centimeters,
            ClassifiedAs = [Aat.Height],
            AssignedBy =
            [
                new AttributeAssignment
                {
                    Label = "Measurement of the Night Watch",
                    CarriedOutBy =
                    [
                        new Group
                        {
                            Id = "https://linked.art/example/group/nightwatchteam",
                            Label = "Operation Night Watch Team",
                        },
                    ],
                    PartOf =
                    [
                        new Activity
                        {
                            Id = "https://linked.art/example/event/operationnightwatch",
                            Label = "Operation Night Watch",
                        },
                    ],
                },
            ],
        },
    ],
    ClassifiedAs =
    [
        new Type("http://vocab.getty.edu/aat/300033618", "Painting")
        {
            ClassifiedAs = [Aat.TypeOfWork],
        },
    ],
};

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.