Microsoft has started to list its Windows Phone Tango upgrade as part of the company's history page for its mobile operating system updates. Build 8773.98, which is currently shipping on European Nokia Lumia 900 handsets, is listed as an update that includes messaging, SIM card contacts, and other improvements.

The software giant does not indicate when the update will be available to existing devices, but Microsoft previously promised it would "start the process of working with mobile operators to bring an update to current customers" after its range of Windows Phone Tango phones launched. The update is a fairly minor one from our experience with the Lumia 900, adding MMS improvements and a new GPS location icon. We have asked Microsoft for a timeline on when existing devices will start to receive the update and we'll update you accordingly.