Rumors have already circulated that a flexible display iPhone or iWatch may be on Apple's list of upcoming products, and that may just be the case after the company poster a job available at the company for someone with "flexible glass" interest.

The company has already shown interest in flexible devices by filing a few patent applications aimed in that direction. A recent job ad and still more patent filings provide further hints that the technology is on Apple's agenda.

The listing, seen by several sites and screengrabbed by9to5Mac before its removal, showed Apple searching for a senior optical engineer to work in the Santa Clara Valley, further fueling rumors that Apple is planning to launch a wearable device that would make use of curved glass-like an "iWatch."

Apple said it's looking for someone to "lead the investigation on emerging display technologies such as high optical efficiency LCD, AMOLED, and flexible display to improve overall display optical performance." The key qualifications included in-depth understanding of optical design, viewing angles, color management, and other elements so the candidate could "[a]nalyze the trade-offs between design, process, optical performance, and implementation feasibility" of such displays.

9to5Mac says it has found two other Apple patents for completely flexible devices that change operating modes when the users bends or twists it.

No one is sure why Apple pulled the listing, but employers often do once a position has been filled.