If nothing else, the Microsoft’s first-generation Surface tablets offered numerous lessons that the the software giant can use to help guide future launches — and one of those launches may be fast approaching. According to a report from advertising network AdDuplex, tablets named “Microsoft Corporation Surface 2” and “Microsoft Corporation Surface with Windows 8.1 Pro” have appeared in the network’s logs. This means that at least one currently unannounced tablet — the “Surface 2,” which the report notes was running Windows RT — has been served ads by AdDuplex’s network, likely while being tested internally at Microsoft. The second entry might refer to the current Surface Pro running the RTM version of Windows 8.1, or it could be an entirely new device.