This is a python module for reading the data from an ID TECH credit
card reader connected via serial port (RS-232) or USB-CDC.  It was
written using an ID TECH Spectrum III MagStripe Only, Insert Reader,
model number SPT3-355-12-1NN0N-0C.

http://www.idtechproducts.com/products/insert-readers/68.html

The serial protocol is documented here (the URL says .html, but it
triggers the download of a PDF):
http://www.idtechproducts.com/download/insert-readers/doc_download/413-users-manual-sptiii-moir-product-family.html

It requires pySerial: http://pyserial.sourceforge.net/