The Atari 400 ($550) and 800 ($1000) were part of a series of 8 bit home computers that sold between 1979 and 1992. Atari 800 had more features such as: 48KB ram VS. 8-16KB, 2 cart slots VS. 1, Mech keyboards VS. membrane.
The computer has a custom co-processor to enable better sounds and graphics (Sprites, Display Lists). The Processor is a 6502 running at 1.79MHz.
Atari computers after this: XL Model 1983, XE Model 1985.
Over 2 Million Atari 8 bit computers sold between 1979-1985.
This computer even came with a few receipts for some of the games. Its very faded and difficult to read.
Sources:
https://en.wikipedia.org/wiki/Atari_8-bit_family
https://www.old-computers.com/museum/computer.asp?c=76