Work on #1411.

src/Services/XMLTransform.php

@@ -82,6 +82,12 @@ class XMLTransform extends ServiceProviderBase {
     }
     $xml->registerXPathNamespace('fits', 'http://hul.harvard.edu/ois/xml/ns/fits/fits_output');
     $fits_metadata = $this->islandoraFitsChildXpath($xml);
+
+    // Get the value of the 'externalIdentifier' element generated by Droid.
+    if ($xml->identification->identity->externalIdentifier['type'] == 'puid') {
+      $puid = $xml->identification->identity->externalIdentifier;
+    }
+
     $headers = [
       'label' => t('Field'),
       'value' => t('Value'),
@@ -94,6 +100,7 @@ class XMLTransform extends ServiceProviderBase {
       ];
     }
     else {
+      $fits_metadata['Droid'] = ['PUID' => $puid];
       foreach ($fits_metadata as $tool_name => $vals_array) {
         $variables['islandora_fits_data'][$tool_name] = [];
         $rows = &$variables['islandora_fits_data'][$tool_name];