A new report has surfaced claiming that Sintek Photronic, a well-known supplier of large touchscreen panels, has sent samples to Cupertino for testing. It is purported that the panels are destined for pre-production versions of a forthcoming touchscreen-based iMac. The latest news adds weight to the rumors circulating in recent months that Apple plans on adding a third iMac model to its current range of 21.5-inch and 27-inch iMac offerings.