diff --git a/commands/CmdFI.c b/commands/CmdFI.c
index 8669ea3c..178fe9ee 100644
--- a/commands/CmdFI.c
+++ b/commands/CmdFI.c
@@ -1452,7 +1452,11 @@ CmdIdentify(w, cmd)
 	return;
     }
 
-    if (CmdIllegalChars(cmd->tx_argv[1], "[],/", "Cell use id"))
+    /* NOTE: Relaxing the definition of illegal characters in cell use IDs */
+    /* by allowing brackets.  Possibly the list can be reduced further.	*/
+
+    /* if (CmdIllegalChars(cmd->tx_argv[1], "[],/", "Cell use id")) */
+    if (CmdIllegalChars(cmd->tx_argv[1], ",/", "Cell use id"))
 	return;
 
     if (SelEnumCells(FALSE, (int *) NULL, (SearchContext *) NULL,
diff --git a/database/DBio.c b/database/DBio.c
index 3f6aca45..6389eb23 100644
--- a/database/DBio.c
+++ b/database/DBio.c
@@ -619,6 +619,9 @@ done:
 	    }
 	}
     }
+    /* Update timestamp flags */
+    DBFlagMismatches(cellDef);
+
     cellDef->cd_timestamp = cellStamp;
     if (cellStamp == 0)
     {
@@ -869,6 +872,8 @@ DBReadBackup(name)
 			name);
 		return FALSE;
 	    }
+	    /* Update timestamp flags from dbCellReadDef() */
+	    DBFlagMismatches();
 	}
 	else
 	{
diff --git a/database/DBtimestmp.c b/database/DBtimestmp.c
index 8143eced..f6900a70 100644
--- a/database/DBtimestmp.c
+++ b/database/DBtimestmp.c
@@ -270,6 +270,16 @@ dbStampFunc(cellDef)
  *	processing.  When DBFixMismatch is called, it will notify
  *	the design-rule checker to recheck both wrongArea, and
  *	the cell's eventual correct area.
+ *
+ * This routine has been modified from a poor implementation.  Previously
+ * the parent def of all uses of the cell being checked would be marked
+ * for a stamp mismatch check.  However, when reading a cell with large
+ * numbers of instances, the list of instances would be parsed for every
+ * instance added, leading to an O(N^2) computation.  Routine DBStampMismatch()
+ * has been broken into two parts.  DBStampMismatch() only records the
+ * area to be checked.  DBFlagMismatches() looks at the parents of each
+ * celldef only once, after all instances have been read.
+ *
  * ----------------------------------------------------------------------------
  */
 
@@ -281,18 +291,32 @@ DBStampMismatch(cellDef, wrongArea)
 					 */
 {
     Mismatch *mm;
-    CellUse *parentUse;
 
     mm = (Mismatch *) mallocMagic((unsigned) (sizeof (Mismatch)));
     mm->mm_cellDef = cellDef;
     mm->mm_oldArea = *wrongArea;
     mm->mm_next = mismatch;
     mismatch = mm;
+}
 
-    for (parentUse = cellDef->cd_parents; parentUse != NULL;
-	parentUse = parentUse->cu_nextuse)
+/*
+ * ----------------------------------------------------------------------------
+ * ----------------------------------------------------------------------------
+ */
+
+void
+DBFlagMismatches(checkDef)
+    CellDef *checkDef;
+{
+    CellUse *parentUse;
+    long count;
+
+    for (parentUse = checkDef->cd_parents; parentUse != NULL;
+		    parentUse = parentUse->cu_nextuse)
     {
+	count++;
 	if (parentUse->cu_parent == NULL) continue;
 	parentUse->cu_parent->cd_flags |= CDSTAMPSCHANGED;
     }
+    TxPrintf("Diagnostic:  cell %s count = %ld\n", checkDef->cd_name, count);
 }
diff --git a/database/databaseInt.h b/database/databaseInt.h
index ae3f0f63..5756c458 100644
--- a/database/databaseInt.h
+++ b/database/databaseInt.h
@@ -199,6 +199,7 @@ extern void DBUndoPutLabel();
 extern void DBUndoEraseLabel();
 extern void DBUndoCellUse();
 extern void DBStampMismatch();
+extern void DBFlagMismatches();
 extern void DBTechAddNameToType();
 
 extern void dbComputeBbox();