Slice Intelligence previously estimated 1 million Apple Watch pre-orders at launch, an average 30,000 Apple Watch sales per day in late May and an estimated 2.8 million total sales as of mid June. The research firm's sales estimates are based on e-receipt data from online shoppers in the United States that opted-in to have their inboxes tracked for email receipts.
To give perspective...
Apple's entire 1st Generation iPod sales hovered around 200,000 units.