Hans Pontar reported success on the sourceforge zd1211-devs mailing list.
The device is branded "Arcor Easy Stick A 50 WLAN" (device manufactured
by SMC for a German ISP - SMC model name: WN4501H-LF-IR). General
information and Windows driver are available under (German only):

http://www.arcor.de/hilfe/neu/index.php?sid=&aktion=anzeigen&rubrik=004018140&id=487

Device details:

USB-IDs: Vendor: 0x083A Device: 0xE503
Chip ID: zd1211b chip 083a:e503 v4810 high 00-1d-19 AL2230S_RF pa0 g--N-
Signed-off-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Tested-by: Hans Pontar <pontar@gmx.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>