Check out an iPhone 5s prototype in an unreleased Black and Slate colorway

The iPhone 5s was available in three color options—White and Silver, White and Gold, as well as Space Gray and Black—but Apple was also testing an unreleased Black and Slate variant.

That’s according to @DongleBookPro, via 9to5Mac, which over the weekend on Twitter shared photographs said to depict an alleged iPhone 5s prototype unit. It was manufactured in December 2012, three months after the iPhone 5 was released, according to the poster.

The prototype device features an iPhone 5-style “slate gray” chassis with several observable differences from production units, such as the matte top and bottom. The prototype unit is not fully exposed due to the protective housing concealing its design.

Photographs of an iPhone 5s prototype in an unreleased Black and Slate color, concealed in a stealth case

If you like these images, you may be also interested in claimed photos from a few years back which purportedly show Apple’s prototype for a crocs-style iPhone 5s case that resembles Apple’s iPhone 5c cases (I’ve embedded one of those images further below).

Apple is known to create special cases for prototype hardware whch prevent others from seeing the design. As an example, we previously saw not only similar stealth iPhone cases, but also security cases with Apple Watch prototypes concealed inside.

Apple’s unreleased iPhone 5c-style cases for the iPhone 5/5s

This is Apple’s usual modus operandi when developing and prototyping new devices, but it’s not bullet-proof—back in 2010, an Apple engineer mistakenly left an iPhone 4 prototype on a bar stool that someone found and sold to Gizmodo. The rest, as they say, is history.

Image Credit: DongleBookPro/Twitter