The 320g with leather seems light for a Tour.
The 340g sounds about right. Dunlop leather is heavy and with lead I can see it getting up to 340g.
Its a bit intriguing though. Are you able to get in touch with the person you bought them from? They might have some answers.
"Tennis is just chess with balls."
Sometimes: Dunlop Biomimetic 300 - Sometimes: Prince Exo3 Graphite 93