As Microsoft prepares to announce a rumored 12-inch Surface Pro 3 tablet, an image of what is reportedly the 12.9-inch iPad Pro has made its way online.

Microsoft will be holding a Surface event on May 20 where the company is expected to announce a Windows RT based Surface Mini and 12-inch Surface Pro 3. We just reported on the Surface Pro 3's alleged specs and pricing configurations ahead of Microsoft's event. It now appears that Apple is once again working on its rumored 12.9-inch iPad Pro, thanks to leaked images of what is reportedly a prototype of the tablet.

The image was discovered [in French] by Nowhereelse.fr and shows what is supposedly the 12.9-inch iPad Pro that was believed to have been put on hold by Apple. The image shows what appears to be the rear case of the iPad Pro and you can get an idea of just how large it will be in the hand. The site claims that the shell in the images is intended to act as a reference design for third party companies creating cases and other accessories for the larger iPad.

We've already seen Samsung enter the large sized tablet market with both the Samsung Galaxy NotePro and Galaxy TabPro tablets earlier this year. Samsung's 12.2-inch tablets haven't impressed reviewers or customers due to being described as being too big, too heavy and too expensive.

In March, Apple had decided to put the iPad Pro on pause and the reported reason was due to large-size tablets not being supported by developers and ecosystems.

The leaked image shows what appears to be the iPad Pro's rear case, which matches the design and camera cutouts of both the iPad Air and iPad mini with Retina display. If the image is legit, we could see Apple enter the large-size tablet market sometime this year and join Samsung and Microsoft's large-size tablet ambitions.

As with all reports of unannounced Apple devices, it's always best to take such reports with a huge grain of salt. We'll be sure to keep you posted on any iPad Pro information as it becomes available.