Firstly Atari themselves put out several more obscure models beyond the
410/1010/XC11/XC12, generally only known in eastern Europe:

XCA12 Program Recorder     -in same case as XC12...Poland
CA12 Program Recorder      -in same case as XC12...Poland
    image: http://membres.lycos.fr/romualdl/images/atari/ca12.jpg
XL12 Program Recorder      -XC12 w/slight changed design. Czech/Slovak/Poland
    box seen here: http://jpecher.sweb.cz/pic/sbirka.jpg
XC13 Program Recorder      -XC12 which was "T2000 ready". Czech/Slovak/Poland

Unlike other microcomputer systems of the time period, only Atari-specific
cassette tape recorders could be used with Atari 8-bit computers.  Several
such peripherals were produced:

Compu-Mate Computer Data Recorder by General Electric (GE, G.E.)
- 3-5148A (unit) / 3-5156 (box)
- "Extend the versatility of your home computer. Atari/Commodore Compatible."
- IFM Interface Module: Atari Computer compatible included
- 1st data cable: Data Recorder <-> IFM Interface or Data Recorder <-> C64
- 2nd data cable: IFM Interface <-> Atari computer SIO connector
- No second SIO port - must be at end of SIO chain.
- Battery operated or uses an external power supply
- switch on the bottom, Atari or "All other computers".
- partial source: http://www.atariage.com/forums/index.php?showtopic=128505

Phonemark PM-4401A Data Recorder
- near clone of XC12
- power - plugs directly into wall, (240v, 50Hz) and has a captive power lead
  in addition to the SIO lead.
- source of info:
  http://commons.wikimedia.org/wiki/File:Phonemark-Atari-Data-Recorder.jpg

Datamark XG12
- absolute clone of XC12
- info source: http://www.atariage.com/forums/index.php?showtopic=128505