diff --git a/app/controllers/object_controller.rb b/app/controllers/object_controller.rb
index df55c748..5d37abd3 100644
--- a/app/controllers/object_controller.rb
+++ b/app/controllers/object_controller.rb
@@ -8,7 +8,8 @@ class ObjectController < ApplicationController
   # Return a zip of all the files if they have access to all the files.
   # This will force a login if any of the files is not access=world
   def show
-    files = Purl.files(druid)
+    cocina = Cocina.find(druid)
+    files = cocina.files
     raise ActionController::RoutingError, 'No downloadable files' if files.none?
 
     files.each do |file|
diff --git a/app/models/cocina.rb b/app/models/cocina.rb
new file mode 100644
index 00000000..73eb2dd0
--- /dev/null
+++ b/app/models/cocina.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+# Retrieves the public JSON (cocina) and extracts data from it.
+class Cocina
+  extend ActiveSupport::Benchmarkable
+
+  THUMBNAIL_MIME_TYPE = 'image/jp2'
+
+  def self.find(druid)
+    Rails.cache.fetch("purl/#{druid}.json", expires_in: 10.minutes) do
+      benchmark "Fetching public json for #{druid}" do
+        response = Faraday.get(public_json_url(druid))
+        raise Purl::Exception, response.status unless response.success?
+
+        new(JSON.parse(response.body))
+      end
+    end
+  end
+
+  def self.public_json_url(druid)
+    "#{Settings.purl.url}#{druid}.json"
+  end
+
+  def self.logger
+    Rails.logger
+  end
+
+  def initialize(data)
+    @data = data
+  end
+
+  attr_accessor :data
+
+  def find_file(file_name)
+    file_sets = data.dig('structural', 'contains')
+    raise(ActionController::MissingFile, "File not found '#{file_name}'") unless file_sets # Trap for Collections
+
+    file_sets.lazy.flat_map { |file_set| file_set.dig('structural', 'contains') }
+             .find { |file| file['filename'] == file_name } || raise(ActionController::MissingFile, "File not found '#{file_name}'")
+  end
+
+  def thumbnail_file
+    data.dig('structural', 'contains')
+        .lazy.flat_map { |file_set| file_set.dig('structural', 'contains') }
+        .find { |file| file['hasMimeType'] == THUMBNAIL_MIME_TYPE }
+  end
+
+  def embargo_release_date
+    data.dig('access', 'embargo', 'releaseDate')
+  end
+
+  def files(&)
+    return to_enum(:files) unless block_given?
+
+    files_from_json(&)
+  end
+
+  private
+
+  def files_from_json
+    data.dig('structural', 'contains').each do |fileset|
+      fileset.dig('structural', 'contains').each do |file|
+        file = StacksFile.new(id: data.fetch('externalIdentifier').delete_prefix('druid:'), file_name: file['filename'])
+        yield file
+      end
+    end
+  end
+end
diff --git a/app/models/purl.rb b/app/models/purl.rb
index c9a64fe8..b954dc76 100644
--- a/app/models/purl.rb
+++ b/app/models/purl.rb
@@ -2,53 +2,5 @@
 
 # PURL API service
 class Purl
-  include ActiveSupport::Benchmarkable
-
   class Exception < ::RuntimeError; end
-
-  def self.instance
-    @instance ||= new
-  end
-
-  class << self
-    delegate :public_json, :files, to: :instance
-  end
-
-  def public_json(druid)
-    Rails.cache.fetch("purl/#{druid}.json", expires_in: 10.minutes) do
-      benchmark "Fetching public json for #{druid}" do
-        response = Faraday.get(public_json_url(druid))
-        raise Purl::Exception, response.status unless response.success?
-
-        JSON.parse(response.body)
-      end
-    end
-  end
-
-  def files(druid, &)
-    return to_enum(:files, druid) unless block_given?
-
-    files_from_json(druid, &)
-  end
-
-  def files_from_json(druid)
-    doc = public_json(druid)
-
-    doc.dig('structural', 'contains').each do |fileset|
-      fileset.dig('structural', 'contains').each do |file|
-        file = StacksFile.new(id: druid, file_name: file['filename'])
-        yield file
-      end
-    end
-  end
-
-  private
-
-  def public_json_url(druid)
-    "#{Settings.purl.url}#{druid}.json"
-  end
-
-  def logger
-    Rails.logger
-  end
 end
diff --git a/app/models/stacks_file.rb b/app/models/stacks_file.rb
index 5a33bcb2..1f4ee6fd 100644
--- a/app/models/stacks_file.rb
+++ b/app/models/stacks_file.rb
@@ -41,8 +41,9 @@ def storage_root
   end
 
   def stacks_rights
-    @stacks_rights ||= StacksRights.new(id:, file_name:)
+    @stacks_rights ||= StacksRights.new(cocina: Cocina.find(id), file_name:)
   end
+
   delegate :rights, :restricted_by_location?, :stanford_restricted?, :embargoed?,
            :embargo_release_date, :location, to: :stacks_rights
 
diff --git a/app/models/stacks_image.rb b/app/models/stacks_image.rb
index 5f5c5834..91be782f 100644
--- a/app/models/stacks_image.rb
+++ b/app/models/stacks_image.rb
@@ -60,8 +60,9 @@ def info_service
   end
 
   def stacks_rights
-    @stacks_rights ||= StacksRights.new(id:, file_name:)
+    @stacks_rights ||= StacksRights.new(cocina: Cocina.find(id), file_name:)
   end
+
   delegate :rights, :maybe_downloadable?, :object_thumbnail?,
            :stanford_restricted?, :restricted_by_location?, to: :stacks_rights
 end
diff --git a/app/models/stacks_media_stream.rb b/app/models/stacks_media_stream.rb
index ae876903..791a928b 100644
--- a/app/models/stacks_media_stream.rb
+++ b/app/models/stacks_media_stream.rb
@@ -15,7 +15,7 @@ def file
   delegate :etag, :mtime, to: :file
 
   def stacks_rights
-    @stacks_rights ||= StacksRights.new(id:, file_name:)
+    @stacks_rights ||= StacksRights.new(cocina: Cocina.find(id), file_name:)
   end
 
   delegate :rights, :restricted_by_location?, :stanford_restricted?, :embargoed?,
diff --git a/app/models/stacks_rights.rb b/app/models/stacks_rights.rb
index 1eec6afc..26677464 100644
--- a/app/models/stacks_rights.rb
+++ b/app/models/stacks_rights.rb
@@ -3,15 +3,15 @@
 ##
 # RightsMetadata interpretation
 class StacksRights
-  attr_reader :id, :file_name
+  attr_reader :cocina_file, :cocina
 
-  THUMBNAIL_MIME_TYPE = 'image/jp2'
-
-  def initialize(id:, file_name:)
-    @id = id
-    @file_name = file_name
+  def initialize(file_name:, cocina:)
+    @cocina = cocina
+    @cocina_file = cocina.find_file(file_name)
   end
 
+  delegate :embargo_release_date, :thumbnail_file, to: :cocina
+
   def maybe_downloadable?
     %w[world stanford].include?(rights.download)
   end
@@ -26,23 +26,12 @@ def restricted_by_location?
     rights.view == 'location-based' || rights.download == 'location-based'
   end
 
-  def embargo_release_date
-    cocina_embargo_release_date
-  end
-
   def embargoed?
-    cocina_embargo_release_date && Time.parse(cocina_embargo_release_date).getlocal > Time.now.getlocal
-  end
-
-  def cocina_embargo_release_date
-    @cocina_embargo_release_date ||= public_json.dig('access', 'embargo', 'releaseDate')
+    embargo_release_date && Time.parse(embargo_release_date).getlocal > Time.now.getlocal
   end
 
   # Based on implementation of ThumbnailService in DSA
   def object_thumbnail?
-    thumbnail_file = public_json.dig('structural', 'contains')
-                                .lazy.flat_map { |file_set| file_set.dig('structural', 'contains') }
-                                .find { |file| file['hasMimeType'] == THUMBNAIL_MIME_TYPE }
     thumbnail_file == cocina_file
   end
 
@@ -51,22 +40,4 @@ def rights
   end
 
   delegate :location, to: :rights
-
-  private
-
-  def cocina_file
-    @cocina_file ||= find_file
-  end
-
-  def find_file
-    file_sets = public_json.dig('structural', 'contains')
-    raise(ActionController::MissingFile, "File not found '#{file_name}'") unless file_sets # Trap for Collections
-
-    file_sets.lazy.flat_map { |file_set| file_set.dig('structural', 'contains') }
-             .find { |file| file['filename'] == file_name } || raise(ActionController::MissingFile, "File not found '#{file_name}'")
-  end
-
-  def public_json
-    @public_json ||= Purl.public_json(id)
-  end
 end
diff --git a/spec/abilities/cocina_ability_spec.rb b/spec/abilities/cocina_ability_spec.rb
index e51bc611..a9b67e01 100644
--- a/spec/abilities/cocina_ability_spec.rb
+++ b/spec/abilities/cocina_ability_spec.rb
@@ -7,7 +7,7 @@
   subject(:ability) { described_class.new(user) }
 
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     allow(image).to receive_messages(image_width: 11_957, image_height: 15_227)
   end
 
diff --git a/spec/controllers/file_controller_spec.rb b/spec/controllers/file_controller_spec.rb
index 2316144d..1eb7c5bf 100644
--- a/spec/controllers/file_controller_spec.rb
+++ b/spec/controllers/file_controller_spec.rb
@@ -5,7 +5,7 @@
 RSpec.describe FileController do
   before do
     allow(StacksFile).to receive(:new).and_return(file)
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
   end
 
   let(:public_json) do
diff --git a/spec/controllers/object_controller_spec.rb b/spec/controllers/object_controller_spec.rb
index fff45b96..c4cffa54 100644
--- a/spec/controllers/object_controller_spec.rb
+++ b/spec/controllers/object_controller_spec.rb
@@ -26,6 +26,7 @@
       context "with downloadable files" do
         let(:json) do
           {
+            'externalIdentifier' => 'druid:fd063dh3727',
             'structural' => {
               'contains' => [
                 {
@@ -102,6 +103,7 @@
       context "with a stanford access file" do
         let(:json) do
           {
+            'externalIdentifier' => "druid:bb142ws0723",
             'structural' => {
               'contains' => [
                 {
@@ -165,6 +167,7 @@
       context "with a stanford access file" do
         let(:json) do
           {
+            'externalIdentifier' => "druid:bb142ws0723",
             'structural' => {
               'contains' => [
                 {
diff --git a/spec/models/purl_spec.rb b/spec/models/cocina_spec.rb
similarity index 78%
rename from spec/models/purl_spec.rb
rename to spec/models/cocina_spec.rb
index de913616..81adb401 100644
--- a/spec/models/purl_spec.rb
+++ b/spec/models/cocina_spec.rb
@@ -2,14 +2,15 @@
 
 require 'rails_helper'
 
-RSpec.describe Purl do
+RSpec.describe Cocina do
   before do
     Rails.cache.clear
   end
 
-  describe '.files' do
+  describe '#files' do
     let(:json) do
       {
+        'externalIdentifier' => 'abc',
         'structural' => {
           'contains' => [
             {
@@ -44,12 +45,12 @@
     end
 
     before do
-      allow(Faraday).to receive(:get).with('https://purl.stanford.edu/abc.json')
-                                     .and_return(double(success?: true, body: json))
+      stub_request(:get, "https://purl.stanford.edu/abc.json")
+        .to_return(status: 200, body: json)
     end
 
     it 'gets all the files for a resource' do
-      actual = described_class.files('abc').map { |file| "#{file.id}/#{file.file_name}" }
+      actual = described_class.find('abc').files.map { |file| "#{file.id}/#{file.file_name}" }
 
       expect(actual).to contain_exactly('abc/26855.jp2', 'abc/123.jp2')
     end
diff --git a/spec/requests/file_auth_request_spec.rb b/spec/requests/file_auth_request_spec.rb
index 53992b68..f8a1d6e5 100644
--- a/spec/requests/file_auth_request_spec.rb
+++ b/spec/requests/file_auth_request_spec.rb
@@ -16,7 +16,7 @@
   let(:sf) { StacksFile.new(id: druid, file_name:) }
 
   before(:each) do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     allow(File).to receive(:world_readable?).with(path).and_return(perms)
   end
 
diff --git a/spec/requests/file_spec.rb b/spec/requests/file_spec.rb
index ff17b8ee..28ad7d41 100644
--- a/spec/requests/file_spec.rb
+++ b/spec/requests/file_spec.rb
@@ -4,7 +4,7 @@
 
 RSpec.describe "File requests" do
   before do
-    allow(Purl).to receive_messages(public_json:)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
   end
 
   let(:druid) { 'nr349ct7889' }
diff --git a/spec/requests/iiif/auth/v2/probe_service_spec.rb b/spec/requests/iiif/auth/v2/probe_service_spec.rb
index e2cb0307..47b516bd 100644
--- a/spec/requests/iiif/auth/v2/probe_service_spec.rb
+++ b/spec/requests/iiif/auth/v2/probe_service_spec.rb
@@ -13,7 +13,7 @@
 
   # rubocop:disable RSpec/AnyInstance
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     allow(File).to receive(:world_readable?).and_return('420')
     allow(StacksFile).to receive(:new).and_call_original
   end
diff --git a/spec/requests/iiif_auth_request_spec.rb b/spec/requests/iiif_auth_request_spec.rb
index b0aeb1d0..bf61ce68 100644
--- a/spec/requests/iiif_auth_request_spec.rb
+++ b/spec/requests/iiif_auth_request_spec.rb
@@ -37,7 +37,7 @@
       allow(http_client).to receive(:get).and_return(instance_double(HTTP::Response, status: 200, body: StringIO.new))
       allow_any_instance_of(IiifController).to receive(:current_user).and_return(current_user)
       allow_any_instance_of(IiifController).to receive(:current_image).and_return(current_image)
-      allow(Purl).to receive(:public_json).and_return(public_json)
+      allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     end
 
     context 'with a public item' do
diff --git a/spec/requests/iiif_spec.rb b/spec/requests/iiif_spec.rb
index 15b05133..24e5a41a 100644
--- a/spec/requests/iiif_spec.rb
+++ b/spec/requests/iiif_spec.rb
@@ -44,7 +44,7 @@
   end
 
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
 
     # stubbing Rails.cache.fetch is required because you can't dump a singleton (double)
     # which is what happens when writing to the cache.
diff --git a/spec/requests/media_auth_request_spec.rb b/spec/requests/media_auth_request_spec.rb
index f3399f01..aa0e985d 100644
--- a/spec/requests/media_auth_request_spec.rb
+++ b/spec/requests/media_auth_request_spec.rb
@@ -33,7 +33,7 @@
   end
 
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     allow_any_instance_of(MediaController).to receive(:current_user).and_return(user)
     allow_any_instance_of(MediaController).to receive(:current_media).and_return(mock_media)
   end
diff --git a/spec/requests/media_headers_request_spec.rb b/spec/requests/media_headers_request_spec.rb
index e542c132..cfddf299 100644
--- a/spec/requests/media_headers_request_spec.rb
+++ b/spec/requests/media_headers_request_spec.rb
@@ -4,7 +4,7 @@
 
 RSpec.describe "CORS headers for Media requests" do
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
   end
 
   let(:public_json) do
diff --git a/spec/requests/metrics_spec.rb b/spec/requests/metrics_spec.rb
index 136b003e..a844b7e2 100644
--- a/spec/requests/metrics_spec.rb
+++ b/spec/requests/metrics_spec.rb
@@ -8,6 +8,7 @@
   let(:file_name) { 'image.jp2' }
   let(:json) do
     {
+      'externalIdentifier' => "druid:#{druid}",
       'structural' => {
         'contains' => [
           {
diff --git a/spec/requests/remote_iiif_image_delivery_spec.rb b/spec/requests/remote_iiif_image_delivery_spec.rb
index 793f72dc..bbb5c0df 100644
--- a/spec/requests/remote_iiif_image_delivery_spec.rb
+++ b/spec/requests/remote_iiif_image_delivery_spec.rb
@@ -35,7 +35,7 @@
   end
 
   before do
-    allow(Purl).to receive(:public_json).and_return(public_json)
+    allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
     stub_request(:get, info_request)
       .to_return(status: 200, body: info_response)
     stub_request(:get, image_response)
diff --git a/spec/services/iiif_info_service_spec.rb b/spec/services/iiif_info_service_spec.rb
index 94159789..545396ce 100644
--- a/spec/services/iiif_info_service_spec.rb
+++ b/spec/services/iiif_info_service_spec.rb
@@ -174,7 +174,7 @@
       end
 
       before do
-        allow(Purl).to receive(:public_json).and_return(public_json)
+        allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
 
         allow(image).to receive(:restricted_by_location?).and_return(true)
       end
@@ -222,7 +222,7 @@
       end
 
       before do
-        allow(Purl).to receive(:public_json).and_return(public_json)
+        allow(Cocina).to receive(:find).and_return(Cocina.new(public_json))
         allow(image).to receive_messages(stanford_restricted?: true, restricted_by_location?: true)
       end