AdDuplex has spotted what it believes could be a pair of new Surface tablets accessing its Windows ad network. The advertising network says it "regularly" sees devices named "Microsoft Corporation Surface 2" and "Microsoft Corporation Surface with Windows 8.1 Pro" viewing its ads. The former device is thought to be running Windows RT, just like the current-generation Surface for Windows RT, but it looks like Microsoft might be ready to drop the "RT" name from the device. While the second tablet, "Surface with Windows 8.1 Pro," could be the company testing a final build of Windows 8.1 on the existing Surface Pro, it could also be the long-rumored hardware refresh that will finally bring Intel's latest Haswell processors to the hybrid tablet.

In the same post, AdDuplex also notes it's found what could be a pair of Nokia tablets accessing its network. It's seen devices named RX-107, -108, -113, -114, -115, and -116, and believes that the model numbers could either be "one device progressing through development stages," or two separate device lines. Sources have already confirmed to The Verge that Nokia is planning to launch a Windows RT tablet, codenamed Sirius, soon.