In our latest look at Windows Phone handset usage from AdDuplex, we see the recently-released Lumia 520 pulling ahead even further and cementing its lead. Plus, the firm provides a peek at how the recently-released Lumia 1020 is fairing.

As you may remember, AdDuplex bills itself as the largest cross-promotion network for Windows Phone and Windows 8 apps, empowering developers and publishers to promote their apps for free by helping each other. And each month it provides a tantalizing glimpse at which Windows Phone (and Windows) devices people are actually using.

Some trends from this month’s report, include:

Lumia 520. As noted last month, Nokia’s strategy of shipping high-quality but inexpensive new low-end Windows Phone 8 handsets is really paying off. The Lumia 520 is still the number one handset overall and its extended its lead this month to 18 percent of all Windows Phones in use, up from 13 percent a month ago. But if you look at just Windows Phone 8 handsets—leaving out 7.x models—the 520 is fully 30 percent of all Windows Phone usage. That is amazing. (In the US, the nearly identical Lumia 521 has 8 percent of the market, good for 4th place.)

9 of the top 10 phones are Nokia Lumias. With the HTC 8X falling to 10th place overall with just 4 percent of usage, the top 10 is nearly all Nokia: The Lumia 520, 920, 620, 710, 800, 820, 720, 610 and 900 fill out the top 9 of 10 phones.

Lumia 1020. Nokia’s new flagship offering, the Lumia 1020, was launched just at the end of July so it’s no surprise that the device barely registers in the charts: It comes in at number 32, or number 16 if you look just at Windows Phone 8 handsets. But AdDuplex says that when you compare the US-only launch of the 1020 to the previous US-only flagship launch—that for the Lumia 920—something interesting emerges: The 1020 is actually doing as well or better over time than its predecessor.

Nokia. The world’s biggest maker of Windows Phone handsets is basically the world’s only maker of Windows Phone handsets. Nokia now accounts for 87 percent of all Windows Phone usage worldwide, compared to 9.8 percent for HTC and negligible amounts for both Samsung and Huawei (2.1 percent and 1.2 percent, respectively).

Windows Phone 8. 65 percent of the Windows Phone handsets in use worldwide are running the latest OS version, while 35 percent are still using Windows Phone 7.x. That’s good news. The bad news: Only 3 percent of those Windows Phone 8 handsets are running the very latest version, GDR2.

512 MB vs. 1 GB. New this month, AdDuplex looks at how much memory is shipping Windows Phone handsets. Thanks I’m sure to the success of low-end devices like the Lumia 520 and 620, 57 percent of Windows Phones in use have 512 MB of RAM, compared to 43 percent with 1 GB.

US carriers. Verizon is still number one in the US with 39 percent of the market, compared to 34 percent for AT&T. But thanks to the release of the Lumia 521, T-Mobile usage has jumped to 19 percent, triggering usage losses in the top two carriers.

Unidentified handsets. With the Widows Phone community awash in rumors of new phones, you may be interested to see that AdDuplex has identified some new phones in testing. These include the Nokia RM-955 (new WXGA device, possibly a 920 or 1020 variant), Nokia RM-937 (a 720p or even 1080p [!] device that is possibly the rumored Nokia phablet), Nokia RM-927 (Verizon version of the 937), Nokia RM-940 (AT&T version of the 937), and the Samsung SGH-I187 (another 720p or possibly 1080p device for AT&T).