provenance/3 matches the site

public static Activity Shared_Ownership()
{
    var purchase = new Activity()
        .WithContext()
        .WithId("https://linked.art/example/provenance/3")
        .WithLabel("Purchase of Painting by Two Dealers")
        .WithClassifiedAs(Aat.ProvenanceActivity);

    purchase.Part = [
        new RightAcquisition
        {
            Establishes = [
                new Right()
                    .WithLabel("Total Right of Ownership")
                    .WithClassifiedAs(OwnershipRight)
                    .WithAppliesTo(Painting)
                    .WithPart(
                        Share("30% Ownership by Dealer 1", 30, "Dealer 1"),
                        Share("70% Ownership by Dealer 2", 70, "Dealer 2"))
            ]
        }
    ];

    return purchase;
}

var activity = new Activity
{
    Context = ["https://linked.art/ns/v1/linked-art.json"],
    Id = "https://linked.art/example/provenance/3",
    Label = "Purchase of Painting by Two Dealers",
    ClassifiedAs = [Aat.ProvenanceActivity],
    Part =
    [
        new RightAcquisition
        {
            Establishes =
            [
                new Right
                {
                    Label = "Total Right of Ownership",
                    ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                    AppliesTo =
                    [
                        new HumanMadeObject
                        {
                            Label = "Painting",
                            ClassifiedAs =
                            [
                                new Type("http://vocab.getty.edu/aat/300033618", "Painting")
                                {
                                    ClassifiedAs = [Aat.TypeOfWork],
                                },
                            ],
                        },
                    ],
                    Part =
                    [
                        new Right
                        {
                            Label = "30% Ownership by Dealer 1",
                            ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                            PossessedBy =
                            [
                                new Group
                                {
                                    Label = "Dealer 1",
                                },
                            ],
                            Dimension =
                            [
                                new Dimension
                                {
                                    Value = 30,
                                    Unit = new MeasurementUnit("http://qudt.org/3.0.0/vocab/unit/Percent", "Percent"),
                                },
                            ],
                        },
                        new Right
                        {
                            Label = "70% Ownership by Dealer 2",
                            ClassifiedAs = [Aat.Term("300055603", "Ownership Right")],
                            PossessedBy =
                            [
                                new Group
                                {
                                    Label = "Dealer 2",
                                },
                            ],
                            Dimension =
                            [
                                new Dimension
                                {
                                    Value = 70,
                                    Unit = new MeasurementUnit("http://qudt.org/3.0.0/vocab/unit/Percent", "Percent"),
                                },
                            ],
                        },
                    ],
                },
            ],
        },
    ],
};

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.