Microsoft’s latest mass market Lumia goes on sale today, Friday, for under £100, and its big brother — the 640XL — appears at the end of the month.

The 640 is this year’s successor to the popular 630/635 models launched last May, while the impressive 640XL is a solid successor to the phablet-sized Lumia 1320, but with much broader appeal and at a lower price.

To confuse an already sprawling portfolio, both new devices have been given the same number, even though they’re quite different propositions.

For the XL, which will cost a shade over £200 in the UK and will be available at the end of April, Microsoft took feedback from business customers with an eye for durable phablet-sized phones:

“The B2B channel wanted larger screen devices but found flagships too expensive,” a Microsoft spokesperson said at a briefing. “The 1320 found its niche heavily in B2B, and they were quite prescriptive with what wanted. They wanted more at a lower price: a slightly smaller screen, a better display and camera, and it’s around $75 to $100 cheaper than the Lumia 1320.”

That budget phablet was announced in October 2013.

The XL (a full review will follow) looks like a unibody device, but has a removable 3000mAh battery, and all models come in a matte finnish, unlike many of the slippery glossy consumer-oriented Lumias. The camera is a well decent 13MP jobbie with Carl Zeiss optics, and one variant for Western markets supports two LTE SIMs at once — a first.

The display is an HD 720 (1280x720) 5.7-inch panel, meaning the pixel density is a lowly 259ppi, but it's excellent outdoors and has Gorilla Glass 3.

The innards are a Snapdragon 400 quad core common across today’s budgets phones. There’s no wireless charging, and unfortunately, no dedicated navigation buttons. Microsoft has yet to get the pop-up “soft” navigation bar quite right.

The 640 (not XL) is likely to sell in greater numbers, as did the successor, the 630, and before that, the 520 (the phone that saved Windows Phone, but didn’t save Nokia).

The new model is fairly similar to the 630/635 but larger (with a 5-inch display) and it adds some of the features left out of last year’s release: automatic screen brightness, a selfie camera, and LED flash. It’s ready for Window 10 with 1GB of RAM, as all Lumias will be, from now on.

So, Microsoft, why give two quite different phones the same model number? Especially since you have so many models around the same price range? Here’s the answer:

“We wanted to make the naming convention easier for consumers,” a Microsoft spokesmen said, and “move away from numbers”.

So if you’re looking at the name “Lumia 640 XL” and think you see the numerals “6”, “4” and “0” you must be mistaken. What you’re actually seeing are pictograms for: a tadpole, a man sleeping in a hammock, and a boiled egg.

So there. ®

Microsoft Lumia 640 Specifications

Microsoft Lumia 640 XL Specifications