diff --git a/src/components/anno-viewer/anno-viewer.html b/src/components/anno-viewer/anno-viewer.html
index 1035a4a..5acfb0d 100644
--- a/src/components/anno-viewer/anno-viewer.html
+++ b/src/components/anno-viewer/anno-viewer.html
@@ -15,6 +15,7 @@
   v-on:mouseover.stop="mouseenter"
   v-on:mouseleave.stop="mouseleave"
   :data-w3-anno-id="annoIdUrl"
+  :data-iana-working-copy="annotation['iana:working-copy']"
   :data-target-fragment="targetFragment"
   >
 
@@ -404,10 +405,8 @@ <h5><span class="fa fa-link"></span>
 
         ><bootstrap-button @click="revise"
           btn-class="default btn-outline-secondary"
-          :icon-fa="isOwnAnno ? 'pencil' : 'medkit'"
-          v-if="checkAclAuth({ isOwnAnno, privName: 'revise_‹own›' })"
-          >
-          {{ l10n(isOwnAnno ? 'edit' : 'edit_as_moderator') }}
+          v-if="editable" :icon-fa="editable.icon"
+          >{{ l10n(editable.voc) }}
         </bootstrap-button
 
         ><bootstrap-button v-else @click="revise" caption="⚙" btn-class="
diff --git a/src/components/anno-viewer/anno-viewer.js b/src/components/anno-viewer/anno-viewer.js
index 3659d74..b0fa57a 100644
--- a/src/components/anno-viewer/anno-viewer.js
+++ b/src/components/anno-viewer/anno-viewer.js
@@ -260,6 +260,31 @@ module.exports = {
       return st;
     },
 
+
+    editable() {
+      const viewer = this;
+      const anno = viewer.annotation;
+      const nonDebugEditable = (function decide() {
+        const { isOwnAnno } = viewer;
+        const auth = viewer.checkAclAuth({ isOwnAnno,
+          privName: 'revise_‹own›' });
+        if (!auth) { return false; }
+        const wCopy = viewer.findVersNumFromAnnoUrl(anno['iana:working-copy']);
+        if (wCopy) {
+          /* Number parsing is necessary: In version history mode, id uses
+            the standards compliant endpoint while working-copy uses the
+            author mode endpoint. */
+          const curVer = viewer.findVersNumFromAnnoUrl(anno.id);
+          if (curVer !== wCopy) { return false; }
+        }
+        return (isOwnAnno ? { icon: 'pencil', voc: 'edit' }
+          : { icon: 'medkit', voc: 'edit_as_moderator' });
+      }());
+      return orf(nonDebugEditable
+        || (viewer.$store.state.uiDebugMode && { icon: 'cog', voc: '' }));
+    },
+
+
     creatorsList() {
       const { creator } = this.annotation;
       if (!creator) { return []; }
@@ -339,6 +364,12 @@ module.exports = {
     },
 
 
+    findVersNumFromAnnoUrl(url) {
+      if (!url) { return 0; }
+      return (+orf(this.$store.state.versionSuffixRgx.exec(url))[1] || 0);
+    },
+
+
     makeEventContext() {
       const viewer = this;
       return {
diff --git a/src/default-config/anno-data.js b/src/default-config/anno-data.js
index 932748e..49a9fa4 100644
--- a/src/default-config/anno-data.js
+++ b/src/default-config/anno-data.js
@@ -49,6 +49,9 @@ const annoDataCfg = {
   // ^- Optional factory function for a function that predicts DOIs
   //    from their anno ID or version identifier.
 
+  versionSuffixRgx: /[~_](\d+)$/,
+  // ^- For guessing the version number from anno ID URLs.
+
   doiVersionSuffixRgx: /[~_]\d+$/,
   // ^- In case the latest version's DOI can be predicted by omitting
   //    a suffix, this is a RegExp that matches the suffix.