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....zugzwang"
Dunlop, Prince....who knows...who cares.