object/letter/2 matches the site

public static HumanMadeObject Order_of_Members()
{
    // This has been copied from the Archives doc examples
    var parent = new Set()
        .WithId("https://linked.art/example/set/archive_sfl")
        .WithLabel("Stieglitz Family Letters");

    var obermeyer = new HumanMadeObject()
        .WithContext()
        .WithId("https://linked.art/example/object/letter/2")
        .WithLabel("Obermeyer 1920");

    obermeyer.IdentifiedBy = [
        new Name("Obermeyer, Bertha (1920)").AsPrimaryName(),
        Identifier.SortValue("000001", parent)
    ];

    obermeyer.MemberOf = [parent];

    return obermeyer;
}

• 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/letter/2",
    Label = "Obermeyer 1920",
    IdentifiedBy =
    [
        new Name("Obermeyer, Bertha (1920)")
        {
            ClassifiedAs = [Aat.PrimaryName],
        },
        new Identifier("000001")
        {
            ClassifiedAs = [Aat.SortValue],
            AssignedBy =
            [
                new AttributeAssignment
                {
                    InfluencedBy =
                    [
                        new Set
                        {
                            Id = "https://linked.art/example/set/archive_sfl",
                            Label = "Stieglitz Family Letters",
                        },
                    ],
                },
            ],
        },
    ],
    MemberOf =
    [
        new Set
        {
            Id = "https://linked.art/example/set/archive_sfl",
            Label = "Stieglitz Family Letters",
        },
    ],
};

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.