The Atari 1050 is the Floppy Disk Drive for the Atari XL models. I have this one connected to the 800XL.
Information:
https://www.atari65xe.com/2019/02/24/atari-1050-disk-drive/
https://en.wikipedia.org/wiki/Atari_8-bit_computer_peripherals
http://www.computinghistory.org.uk/det/11991/Atari-1050-Disk-Drive/
http://www.atarimuseum.com/computers/8bits/xl/xlperipherals/atari1050.html
http://www.atarimania.com/faq-atari-400-800-xl-xe-what-is-the-atari-1050-disk-drive_28.html