Both version of the Microsoft phone Microsoft Lumia 640 (both single-SIM and dual-SIM) are getting the prices cut, making them attractive Windows 10 mobile phones. The price is now $79 for the unlocked 5-inch Windows 10 phone Lumia 640: https://www.amazon.com/Microsoft-Nokia-640-Unlocked-Smartphone/

Lumia 640 phones are updated to run Windows 10 Mobile OS even though they were launched with Windows Phone 8.1 with Lumia Denim in March 2015.

The Microsoft Lumia 640 phones have a 5-inch screen, with a 1280×720 resolution display with ClearBlack technololgy for deeper black colors. They are powered by the quad-core 1.2 GHz Qualcomm Snapdragon 400 processor, with 1GB RAM, and 8GB storage, but with 128GB microSD card expansion support.

The Lumia 640 battery life gives these phones 17.5 hours of 3G and 26.5 hours of 2G talk time, and 36 days of stand-by time, from the replaceable 2500 mAh battery. The weight is 145 gram, and thickness is 8.8 mm.

The front camera is a 0.9MP cam, while the rear camera is a 8MP cam.

Network support is for: GSM network: 850 MHz, 900 MHz, 1800 MHz, 1900 MHz.
WCDMA network: Band 5 (850 MHz), Band 8 (900 MHz), Band 1 (2100 MHz). And LTE FDD network: Band 8 (900MHz), Band 20 (800MHz), Band 1 (2100 MHz), Band 3 (1800 MHz), Band 7 (2600 MHz).

Other connectivity options available are 802.11 b/g/n Wi-Fi, Bluetooth 4.0, and a micro-USB 2.0 port.

And the sensors in this Windows phone include GPS, A-GPS, A-GLONASS, BeiDou, sensorcore, magnetometer, accelerometer, proximity sensor, and of course ambient light sensor.

Microsoft Lumia 640 was succeeded by the Microsoft Lumia 650 that was launched in February 2016.