Apple has reportedly received PCBs from Flexium Interconnect, Carrer Technology and Zhen Ding Technology Holding. Reports suggest that the tech giant will examine the parts before approving them for the iWatch. Zhen Ding is Apple's largest supplier of printed circuit boards, and plans to spend over $100 million to add production capacity. The PCB manufacturer expects orders not only for the iWatch, but also for the iPhone 6 and iPhone phablet.

"Apple is likely to introduce 'iWatch' in 2014. From our channel checks, Inventec is the major assembly source for 'iWatch', with about 60% of order allocation," said CIMB Securities analyst Wanli Wang in a report. CIMB projects 63.4 million units of "iWatch" shipments in the year after its launch with an average price of around $199, while the "iWatch" project is estimated to contribute 19% of Inventec's earnings in 2014, Wang said.

Taiwan's Apple Daily newspaper said Quanta Computer was splitting the "iWatch" orders with Inventec by taking 40 percent of order allocation, citing unnamed sources. California-based Apple last month filed a trademark application for an "iWatch" in Japan. Apple chief Tim Cook earlier this year forecast that there will be "tons of companies playing" in the wearable computing sector.