Apple will unveil the iPhone 11 series next week, likely alongside new Apple Watch models, but these aren’t the only new iOS products the company is developing. In fact, some of them might not be introduced until a much later date, and we’re not talking about the 2019 iPad Pro models that should be announced in October. A discovery in an internal iOS 13 development build suggests Apple hasn’t stopped developing its rumored augmented reality (AR) glasses, revealing some details about the unreleased device.

The AR glasses, which we’ve called Apple Glasses in the past because of Apple’s way of naming some of its products under Tim Cook, have made appearances in previous rumors. Several well-known insiders familiar with Apple’s plans claimed in the past few years that Apple is indeed developing AR glasses, which should be unveiled in 2020 at the earliest.

Since then, we saw Apple turn AR into one of the main features of iOS, with each new software release, including new AR tricks. This has been seen as proof that Apple is laying the foundation of what will eventually become the operating system of Apple Glasses, which will probably be based on iOS. These Apple Glasses should work as a companion device, at least at first, requiring a connection to an iPhone to operate, just like the Apple Watch does.

With a few days left until Apple releases the final version of iOS 13, MacRumors inspected an internal development build of the upcoming operating system. That’s where it spotted a STARTester app that can switch in and out of a head-mounted mode “presumably to replicate the functionality of an augmented reality headset on an iPhone for testing purposes.” The test includes two modes, “worn,” and “held,” which further supports the idea that it’s a test for AR glasses.

Furthermore, an internal “Readme” file in IOS 13 describes a “Starboard” system shell for stereo AR apps, which also implies the use of a headset. The same file indicates that Apple is developing an AR device called “Garta,” which could be one of many prototypes, MacRumors says.

The “Starboard mode” is also referenced elsewhere in the code, with “views,” and “scenes.” Some of these strings mention AR clearly, like “ARStarBoardViewController” and “ARStarBoardSceneManager.”

There are no images for these Apple Glasses prototypes, and no official timeline for their launch. Apple doesn’t talk publicly about whatever projects it may have in development, but Tim Cook did say in the past the company is working on products that haven’t been rumored.